Please advise.13k cash needed to pay past due 37k loan balance. 110k ARVMonthly payment 409RENTs FOR $1000owner just needs $1000 to move outfirst, is this a good deal?

Not a lot of decisions, other than how much to pay the seller above and beyond the mtg balance.  

1) They will trust their attorney over yours;2) In the case of a dispute, courts typically take sides against the party that drafted the agreement.3) They will bear the balance of the expense. 

Just gotta find that right balance.

I have will have put in about a total of $15K in repairs and updates when complete.Current numbers are:PITI (fha loan so that includes pmi) $1038/moLoan balance $112K (30 yr ln - right at 23 years left on term)ARV $158-160KExpected rental income: $1700/moExpenses:Vacancy:$80.00Repairs:$80.00CapEx:$112.00Garbage:$20.00Management:$144.00

But the sweet spot is in the lower end of the market, and that is a fine balancing act between nice tenants and low price; increased cash flow...and still aiming for appreciation. 

I was thinking to offer the seller 100k cash then he finance the balance of 3-5/30 amortization.

You could use the retained boot along with the equity to balance the equation.  

That way you don't lose TONS of money with:Hard money WILL have regulations on credit and incomeYou will have to get an appraisalYou will have to show experience with previous investment properties (My area requires 4 deals)You WILL owe that balance at the end of the term (If not you will get buried in extension fees) POINTS!

Mike Creswell is correct that you need to find a portfolio lender (a.k.a. balance sheet lender) to work with.