intel core i7 2020 will it be outdated

There is no way to know when some future release of macOS will drop support for Intel processors. Most people are guessing 3-5 years from now. The last major transition, from PowerPC to Intel processors, happened gradually over 7 years (2006-2013) but even then some older models were dropped from support each year.

If you are thinking of buying for the long term (8-10 years) then Apple Silicon (M1, M2) is the way to go. For intermediate term (about 5 years) you should be fine with an Intel Mac.

I would not buy a refurbished or older Mac from anywhere other than Apple or OWC (MacSales.com). There are too many out there that are not prepared properly and the buyer ends up with a non functioning Mac.

If the budget permits I'd get a 24" M1 iMac with 16 GB RAM and a 1 TB SSD. Also get one with Ethernet so you can connect to the internet via Ethernet rather than WiFi. WiFi is a problem when downloading and installing system updates/upgrades as it can have drop outs and is much slower than Ethernet.

A 2020 Mac can run Ventura and probably 2 system after that. My 2017 iMac runs Ventura without issue. At it's at the 5 year mark it may or may not be able to run the next system to come down the line. We'll just wait and see.

Eventually. It can run the current version of macOS, i.e. Ventura.