Not a big business but still we take care of both sides properly to avoid turn over rates to increase more return to the owners by taking care of tenants quickly and rightly.

You will increase your cash flow investing in multi unit purpose built properties and will likely be looking at a commercial mortgage.Purpose built multi unit rentals is you best option to grow your investments and your income. 

Given I'm looking for buy and hold for over 10 years would you recommend this deal as good deal.If I assume conservative 1% appreciation and 2% rent increase, I get around overall 9.5% return over 10 years.  

You'll need to run sprinklers throughout the house (costly for a number of reasons, especially if you have to increase the water main size), have an enclosed trash area with a drain, have electrical exist signs at the egress points in the house, and they will ultimately require you to become ADA compliant.

Can you offer any tips on refinancing mobile home and RV parks after expanding and increasing occupancy?

Also look at the potential rates and with the same calculation that’s the value that you could add to the property by doing some rehab and increasing the rents.

Now that rents are increasing he is looking to buy. 

I highly doubt this place will appreciate anytime soon.No rent increases in sight.

If I only use the $1480 towards the mortgage payment, the time frame would be considerably longer than 3 years, that's why I don't mind paying the $500.

(rents are increasing in the area, but we are heading into fall/winter where the tenant pool is lower) Assume that you would get pretty much all your money out on the refi.