6 GB Ram
Not sure if the above will run GTA V at max or at all as i don't know the requirements yet. I've had my current PC since 2009 and have noticed i can no longer run some of the newest games at max settings so i'm sure i'll upgrade soon.
I do own both consoles as well though so if my PC wasn't able to handle GTA V i'll play on console until i upgrade. The last 2 years i have only bought games for my PC and here in the UK PC games are normally £10-£15 cheaper than console so the money i've saved from that will help in upgrade costs.
Just waiting for GTA V to actually release now...