i dont have enough RAM to upgrade my mac mini to Snow leopard help?

All Intel processor MacMini's can be upgraded to 10.6.8

If you do a Apple Menu > About this Mac > More information for System Profiler (or open that in Utilities) and tell me the Mac identifier (ex: MacMini 4,1) I can tell you the exact RAM specs and amount you can put in.

Or you can find the 10.5 version of MacTracker and they will tell you.

Be warned, if your doing this to get to a later OS X version like 10.7+, that your PPC based software WILL NOT WORK.

For a 10.5 era issued machine, I just advise you stick with 10.6.8 max and get a new Mac if you need something like iCloud etc as Apple is going to issue a new 10.9 shortly anyway and it will disqualify more older machines.

OS X 10.4/10.5 need to upgrade, 10.6.8 ok still