Q: renaming home folder

Best is to do this and start over.

What to do before selling or giving away your Mac - Apple Support

The OSX and apps ae locked to Apple ID used to "purchase" them and the password for that ID has to be entered to update them

Before acquiring a second-hand computer, you should have run Apple Diagnostics or the Apple Hardware Test, whichever is applicable.

The first thing to do after acquiring the computer is to erase the internal drive and install a clean copy of OS X. You—not the original owner—must do that. Changes made by Apple over the years have made this seemingly straightforward task very complex.

How you go about it depends on the model, and on whether you already own another Mac. If you're not sure of the model, enter the serial number on this page. Then find the model on this page to see what OS version was originally installed.

It's unsafe, and may be unlawful, to use a computer with software installed by a previous owner.

1. If you don't own another Mac

a. If the machine shipped with OS X 10.4 or 10.5, you need a boxed and shrink-wrapped retail Snow Leopard (OS X 10.6) installation disc from the Apple Store or a reputable reseller—not from eBay or anything of the kind. If the machine is very old and has less than 1 GB of memory, you'll need to add more in order to install 10.6. Preferably, install as much memory as it can take, according to the technical specifications.

b. If the machine shipped with OS X 10.6, you need the installation media that came with it: gray installation discs, or a USB flash drive for a MacBook Air. You should have received the media from the original owner, but if you didn't, order replacements from Apple. A retail disc, or the gray discs from another model, will not work.

To start up from an optical disc or a flash drive, insert it, then restart the computer and hold down the C key at the startup chime. Release the key when you see the gray Apple logo on the screen.

c. If the machine shipped with OS X 10.7 or later, you don't need media. It should start up in Internet Recovery mode when you hold down the key combination option-command-R at the startup chime. Release the keys when you see a spinning globe. Note that Mac Pro tower models older than late 2014 (with the "cheese-grater" enclosure) cannot use Internet Recovery, regardless of which OS version they shipped with. The round Mac Pro (2014 or later) can use it.

d. Some 2010-2011 models shipped with OS X 10.6 and received a firmware update after 10.7 was released, enabling them to use Internet Recovery. If you have one of those models, you can't reinstall 10.6 even from the original media, and Internet Recovery will not work either without the original owner's Apple ID. In that case, contact Apple Support, or take the machine to an Apple Store or another authorized service provider to have the OS installed.

2. If you do own another Mac

If you already own another Mac that was upgraded in the App Store to the version of OS X that you want to install, and if the new Mac is compatible with it, then you can install it. Use Recovery Disk Assistant to prepare a USB device, then start up the new Mac from it by holding down the C key at the startup chime. Alternatively, if you have a Time Machine backup of OS X 10.7.3 or later on an external hard drive (not a Time Capsule or other network device), you can start from that by holding down the option key and selecting it from the row of icons that appears. Note that if your other Mac was never upgraded in the App Store, you can't use this method.

3. Partition and install OS X

a. If you see a lock screen when trying to start up from installation media or in Recovery mode, then a firmware password was set by the previous owner, or the machine was remotely locked via iCloud. You'll either have to contact the owner or take the machine to an Apple Store or another service provider to be unlocked. You may be asked for proof of ownership.

b. Launch Disk Utility and select the icon of the internal drive—not any of the volume icons nested beneath it. In the  Partition tab, select the default options: a GUID partition table with one data volume in Mac OS Extended (Journaled) format. This operation will permanently remove all existing data on the drive.

c. An unusual problem may arise if all the following conditions apply:

          OS X 10.7 or later was installed by the previous owner

          The startup volume was encrypted with FileVault

          You're booted in Recovery mode (that is, not from a 10.6 installation disc)

In that case, you won't be able to unlock the volume or partition the drive without the FileVault password. Ask for guidance or see this ASC discussion.

d. After partitioning, quit Disk Utility and run the OS X Installer. If you're installing a version of OS X acquired from the App Store, you will need the Apple ID and password that you used. When the installation is done, the system will automatically restart into the Migration Assistant, which will prompt you to transfer the data from another Mac, its backups, or from a Windows computer. If you have any data to transfer, this is usually the best time to do it.

e. Run Software Update and install all available system updates from Apple. To upgrade to a major version of OS X newer than 10.6, get it from the Mac App Store. Note that you can't keep an upgraded version that was installed by the original owner. He or she can't legally transfer it to you, and without the Apple ID you won't be able to update it in Software Update or reinstall, if that becomes necessary. The same goes for any App Store products that the previous owner installed—you have to repurchase them.

4. Other issues

a. If the original owner "accepted" the bundled iLife applications (iPhoto, iMovie, and Garage Band) in the App Store so that he or she could update them, then they're irrevocably linked to that Apple ID and you won't be able to download them without buying them. Reportedly, Mac App Store Customer Service has sometimes issued redemption codes for these apps to second owners who asked.

b. If the previous owner didn't deauthorize the computer in the iTunes Store under his Apple ID, you wont be able to  authorize it immediately under your ID. In that case, you'll either have to wait up to 90 days or contact iTunes Support.

c. When trying to create a new iCloud account, you might get a failure message: "Account limit reached." Apple imposes a lifetime limit of three iCloud account setups per device. Erasing the device does not reset the limit. You can still use an iCloud account that was created on another device, but you won't be able to create a new one. Contact iCloud Support for more information. The setup limit doesn't apply to Apple ID accounts used for other services, such as the iTunes and Mac App Stores, or iMessage. You can create as many of those accounts as you like.

Great general advice above.

Specific to remaining the Home Folder, DON'T do it.

Instead, create a new Home Folder that meets your needs, and eventually delete the old one.

Renaming Home folder is fraught with peril, including suddenly not being able to sign in.

When you create a user account on a Mac a matching home directory is automatically created with the same name as the short name used as part of that user account. So if your full name is "John Smith" and your short name is "jsmith" then the home directory will be named jsmith as well.

It is possible to change the both the short name and the home directory name either together or separately but this is deliberately and quite rightly a hidden feature. As per the comment by Grant Bennet-Alder this is a potentially dangerous step if you don't know what your doing.

If you really, really feel you need to rename it then here are two approaches to take.

First, make sure you have a backup of your Mac, you should always have a backup.

Option 1

1. Create a second user account with admin privileges - this is done in System Preferences -> Users & Groups
2. Log out and then back in as this new temporary user
3. Open System Preferences and then click on Users & Groups
4. Select the old user account
5. Hold down the Control key on the keyboard and click on the old user account (or right click) an option labelled 'Advanced Options..." should appear, select this
6. A new dialog will now appear in which you can change the users short name and/or the name of the home directory
7. If you change the name of the home directory you now need to do the following additional steps
8. Run Terminal.app which is in the Utilities folder which is in the Applications folder
9. Type cd /Users
10. Type sudo mv oldhomename newhomename
11. Then log out and log back in as the modified user

Option 2

1. Create a second user account with admin privileges - this is done in System Preferences -> Users & Groups
2. Log out and then log back in as this new temporary user
3. Now run Terminal.app which is in the Utilities folder which is in the Applications folder
4. Type cd /Users
5. Type ls -l
6. It should list the contents of the Users directory and in it should be at least three folders, one for each user account, and a special one called "Shared"
7. You can now do sudomv oldhomename newhomename and substitute the appropriate values, the new name cannot contain a space
8. Now in Users & Groups delete the old user, because you have renamed the home directory it will not find a matching home directory so that will not be deleted
9. Now in Users & Groups create a new user with the short name the same as the new home directory name as you chose above, you optionally can give this new user admin rights
10. Now in Terminal.app do sudochown -R newhomename newhomename strictly speaking what you are actually doing is sudo chown -R newshortname newhomename but because they are the same actual name it does not make a difference, I merely say this for the benefit of pedants
11. Log out of your temporary account
12. Log back in as your renamed account