Where To Start?

I recently found a nice park for sale. It has 6 acres of land, 10 homes, and 10 empty lots ready for homes. Each lot has an individual septic tank and meter pole. The park also has two working deep wells. The homes are in good shape and it is in a really quiet country setting. It also has a pond on the property. The homes are all rented at 325 per month. Avereage lot rent here is around 125 per mnth with the landlord paying 17.50 per unit out of that for trash pick-up. The original asking price was 245,000.00 but has just been dropped to 199,000.00. The owner has offered me owner financing but wants me to make an offer first and give him my terms and conditions and we will negotiate from there. I have access to free delivery and set-up on homes and many very cheap repos. My question is what would be a good offering price and what conditions on the financing??? The worst he can do is tell me no and try again.