As others have said, typically NOI and a resulting CAP rate on determines the value on multi-family properties, which are defined as 5+ units. 

However, they typically cannot owner occupy. 

I can tell you from experience underwriting deals for a number of institutional and semi-pro investors that they have achieved IRRs greater than 15% and yields greater than 8% in markets like San Francisco, LA, NY, and DC that advertise 4% cap rates.Markets with low cap rates typically share the following characteristics:1) Strong rent growth, driven by2) Strong population growth, driven by3) Strong job growth4) Low vacancy5) High per bed rents (lower operating costs as a percentage of total rent)6) Good property management options7) Higher quality tenants (young professionals like myself will rent in SF until their late 30s to early 40s)To achieve returns in these markets, investors buy buildings with significant value-add or development opportunities on very low to no leverage (debt), and refinancing the deal after stabilization to cash out.

I don't know about Tennessee, but typically you would have to honor the lease of the previous landlord.

Most older houses actually are more structurally sound due to higher grade of lumber that was typically used back then.

Typically either the seller or buyer will know how much you will make in many situations with regards to wholesaling the home inside of a pre-existing community.

REO agents typically are barred from doing both sides of the deal on REO listings.

Typically with commercial properties, only the income and the equity is considered for qualifying.  

Figure out the After Repair Value (ARV) - this is the amount the house will typically sell for in excellent condition to an owner occupant.

Over time the amount you need down may vary but typically 20% is expected.