One other to note...
If you look at a fat ps3, before you buy it, pay attention to the noise level. If its loud from the fans, don't buy it. If its quiet, you should be ok. Some of the fats had heat issues and that's the root of all the other problems. The noise level is an indication of this.
I have had a noisy/loud fat ps3 that die with a YLOD and a quiet one that works perfectly. Stay away from a loud one, period.
A good way to test it is to play a bluray disc in it for about 10-15 minutes. If the fans don't kick in crazy loud, then you're probably safe.
A slim will be safest. But I totally understand if the budget prohibits buying a slim. I bought my quiet fat used and it's worked flawlessly for a long time.
Good luck!