From a liability standpoint, the contractor should be thoroughly vetted through the Construction Contractor's Board. Make sure that the contractor has no complaints or other Board action. If the home is to be sold on an installment contract, make sure a current form of security agreement is used. Make sure the lien is properly filed with the Department of Consumer and Business Services and appears on the title to the purchaser's home until it is paid off. Make sure the Bill of Sale and, if applicable, the retail installment contract, both have extensive AS-IS language, making no express warranties and disclaiming all implied warranties. Make sure the buyer gets their own inspection of the home, inside and out, including all systems such as plumbing, electrical, HVAC, etc. I don't recommend letting the buyer waive the inspection - it could come back and bite the landlord if an unknown defect is later found. The landlord wants the buyer relying on his own expert, not on anything the landlord says. After the sale the landlord does not want any lingering liabilities.
The landlord may likely have to be licensed as a dealer under ORS 446.003(8). Review ORS 446.616 for the rules concerning transfer of an interest in a manufactured home. Review ORS 446.611 for the rules regarding perfecting a security interest in the home. See ORS 446.641 regarding notification to the county of a transfer of ownership in the home. The landlord should be careful to record his interest first once it is acquired - and make sure title is clear when he first receives it. Otherwise, he may find himself trying to transfer an interest that the public records show belongs to his predecessor and/or has unreleased liens on it.