BiggerPockets, I need help drafting an Owner Financing Proposal...never done it before.

Details:  I have the opportunity to purchase 3 Condos in a nice complex for $105,000 total from the same owner.  They agreed to owner financing along with a credit check; they want to know my terms?

My questions to you:

1. Recommended down payment? Should it be a percentage?  

2. What is the going interest rate (understand it is negotiable but is it usually above conventional rate or below?)

3. Average loan term for owner financing?

4. What else should I be thinking about?

Is this offer too off?

1. $10,500 down payment (10%)  

2. 5% interest rate 

3. 20 year amortization schedule with option to pay it off sooner

That NETs me $364/month in positive cash flow which I'm good with (ROI = 44%)

Thanks in advance for any assistance or deals that you've done.  Was thinking, should I submit two offers; higher asking price with lower interest vs lower asking price with higher interest?

Thanks

Chris