MH Purchase - Owner Financing Arangement Deal or no-Deal?

I have an opportunity to purchase another rental property. The property is in probate and they want to settle the probate property(land only). The MH on the property is owned by one of the family members(paid in full). The deals:

Land = 12,000 - I pay cash for the land and get the deed
MH = 2006 DW excellent condition =20,000 owner financing at 7% for 15 yrs 0 down
Projected rent = 700 monthly
Ext expense and pymt = 230 monthly
PCF = 470 monthly

I have two deals going on. I will be at the lawyers office to close the land deal an transfer the deed. Should I pay the same lawyer to structure the MH agreement or use a basic contract with the owner and have it notorized or take care of everything at the lawyers office. Also would a lease-option on the MH have any benifit?