Is It Possible to Have More Units To Be Rented to Tenants?

I would actually suggest not using For Rent related cheats at all, until EA has addressed the problem with some games getting corrupted. My suspision is that majority of those affected were using cheats to exceed the limits set by the game. This also goes for cheats allowing for more than 99(?) rental units per save. Personally I never recategorize a rental lot, because I think this might be part of the problem, too ;) So, make sure the rental lot is completed before setting those units, and don't try to revert it to regular residential afterwards.

IF you don't mind starting over occasionally, with a brand new save, I see no problem though. You could also test the cheat in a separate save, in case you have a main save. No matter what you do, remember to backup your current files :)