As a business with expenses, taxes, insurance, non-paying tenants, maintenance and an empty rehab trailer haulaway he is probably clearing $500 a month +/-. 

ALWAYS scope the sewer line on any property you're trying to buy (a new sewer main is expensive).

Not sure about Florida but it can be difficult and expensive to find landing spots for an RV extended periods of time. 

This generally means that the rehabilitation costs must exceed a certain percentage (often 100%) of the building's adjusted basis.Qualified Rehabilitation Expenditures: These are the expenses directly associated with the rehabilitation of the building.

I've had several bids for similar work in the past and pipe bursting seems to be a fairly expensive option.

Even if you end up paying for some of the mortgage, it will help you eliminate or lower your largest expense: housing.

I was able to BRRRR four properties there and now i am slowly deciding to pivot to tackle more appreciation plays.If your first rental is an appreciation play and there simply is not enough rental income to offset your expenses then you may run into financing issues after your first property.

Obviously, newer homes are the "safest" bet because they will likely not need any major CapEx expenditure.What's the oldest property you would consider investing in for rental property before major systems (electrical, plumbing, etc.) become a major liability and expense?

Would it be a good idea to pay for the downpayment on a house that’s less than $100,000 and let my lender cover all the other expenses since I paid for the downpayment and I don’t have to pay them back, but I still have to pay the cost of the house and rehab, etc.?

You can hire someone to do all this and it will probably still be less expensive than LVP.