Owner Financing of 2nd Home/vacation rental

[GL L.]

Hello,

I have been in market for  condo in a particular resort style community.  I found someone who is selling and can probably handle owner financing.   I do have down payment but I really need to get primary home refinanced and get the great deal of equity out  of it  to buy this 2nd condo  free and clear.  I don't want to lose this deal as this will be my 2nd home / income property as vacation rental.  Here my questions

•    I know I will have issues getting refinance for primary property  if the see this owner finning taking place.  Not sure how  to handle this.   Any suggestions
• I have a feeling he owns this condo free and clear or at least very low loan amt.  I feel confident he will do owner financing if I approach it right.  Not sure how to go about and terms  to offer.  I am in position to put down 10-20% and pay  cash in full with in year.  But not sure that is a good approach and would prefer not to tie up all my money in one property.   
• What  about interest? How is that handled if owner financed for least financed, say a year?   
• I really want to put my best foot forward but would also like to try and get some ROI if decide to sell in year or so or get refinancing. Please give me a best case scenario for Him and another best cash scenario for me. So I can get an idea on what to offer him.
• I know I will be paying  near retail as it is on way up and potential for high income producing property  as a very successful resort community and town.   I may even consider over paying just to get it furnished... etc..  

Thanks for the help in helping me thing through these things.