Best place to look for rental property to rent is Craigslist, local newspaper (both print and online) and local property management websites. MLS also have rental properties - check with your local real estate agents.
Best place to look for rental property to purchase is to contact your local real estate agent - residential Realtors if you are looking for town homes, condos, single family residences, multiple units (especially the 1-4 units) or certain apartment complex.
For major apartments for sale, you might want to check into commercial property sites.
Hope this helps.