I am not certain for personal mortgages, but I believe 1 year is the most common and have heard 6 months as well.

How do i structure a deal of this kind, I think im going to target For rent by owners, if we cant come to an agreement on a cash offer, what do i do to set up seller financing?

Technically there are FHA programs for 5+ units but not the kind you're thinking of.  

You are in the right place- there are plenty of free or low cost resources on this site that can help you determine the kind of real estate investing you want to do, the area you want to be in, etc. 

Thank You Kindly

Take some time and learn the market and see what kind of activity is going on.

Is this common?

Unlike passive rental income, the income from an active trade or business is subject to self employment tax (a nasty 15% tax commonly referred to a "social security and medicare" by working folks).

You'd do the work, gain experience and avoid some common pitfalls.

I also don't know how much I can stomach any kind of legal battle.