the best advice that I can give is for you to talk to a local attoreny about the best entity for the four of you to use. Basically, you'll want to either do a C corp, and S corp or an LLC. If you use an LLC, discuss the advantages/disadvantages of being taxed like an S Corp.
I agree with what everyone was saying about get trained in the business before you get started. Then decide on what type of rentals are you looking for? Are you looking for blue collar cheaper homes; Section 8 rentals; median price bread and butter homes; resort properties, etc.
Learn abut your profit centers. For the most part, rental properties are about long term wealth building more so than about significant cash flow today. Are you all on board with that?
Learn to buy properties at a discount, but that are still in good shape. My favorite is to buy a house subject to the existing financing so that I don't have to get new financing, and I keep the mortgages off my credit report while still helping the distressed seller.
Just be sure you understand the end before you get started.