Seller financing. How should I fund rehab?

I was offered seller financing on a property and am curious of two things. What should I negotiate for as far as term, interest, etc?  Secondly the property needs about 40k worth of work to get it rent ready. I'm looking for creative options to get this done. 

Home depot project loan? 

Heloc on the property? (can I do that right away?)

Private lending website? 

Any other creative avenues? 

We would like to keep this property as a buy and hold.

However we do have a HML lined up who will finance 75% arv including rehab and purchase price. Worst case scenario we just use him and flip it.