You really have two different two different functions in this park: 1) manager (collect rent/sell homes) and 2) rehabbing the homes. They require two totally different people and compensation plans.
The manager should receive free lot rent and around $500 per month, and would need to come from one of those 8 tenant-owned homes, as you need someone who is a "stakeholder" in the park and has something to lose if the park does not turn around (namely their equity in their home). I would select the homes that show the best pride of ownership and talk to the owners. Ask them "hey, I'm curious what you think of the park?" and they say "it needs a lot of work but it's a great place to live" then they are a candidate. Their job will be to collect rent, sell or rent homes, and report on the success or failure of the group that is renovating the homes.
The group renovating the homes should give you a firm price on each home being fixed, and never be paid by the hour. Do not pay them a penny except when they are done, and the home has been inspected by the manager and then seen by yourself via smart phone photos. This person or group will need to be insured (either independently or on your policy). The "young guy" you are describing sounds like he is paid by the hour and has no insurance. That's a terrible combination for this job. Remember that the rehabber should only stick around until the homes are completed, and then be off the property immediately. Theirs is not a job but simply a short-term function.
When you say "the cost of both of them is minimal" that concerns me as the number of lawsuits against park owners by employees is soaring, most of which revolve around not getting minimum wage for the hours worked. Make sure that hours are accounted for and that you are not at risk for someone claiming that they are underpaid.
My bet is that you have to replace both people you currently have. The old manager needs to go simply because they were in charge when the park failed. The young guy because he does not sound like a legitimate rehabber. We are big believers in the "pro" vs. the "schmo" -- we use only real people who have real insurance and real references. Using some hack that appears cheap always ends up costing you several times more than the pro when you add in poor work quality, failure to meet the ordinances, unhappy tenants and litigation.