Hello Bryan,
I too am interested in MHP's from the standpoint of the value of individual units and personal property tax liens.
I don't have any idea what lot rents should be in NC, but in Colorado, the same lot would cost a tenant between $450 and $550 per month more than likely. The competition in the immediate area should provide good data on what the market rent should be, but suspect as well that one needs to compare apples to apples and include the effects of amenities. Larger parks probably have swimming pools, clubhouses, offer storage sheds, etc.
On your numbers, I think you might be a bit light on current value, but my opinion is based on a 10% cap rate calc, which might value it at around $80K. My other litmus test comes from my prior cable days, which might place it at 9X to 11X cashflow (NOI), which also places value very near $80K.
The capital improvement required in the water distribution system seems like a no-brainer, but absent separate metering, I wonder if you could immediately divide the water bill by the current quantity of tenants and have them begin to pay this immediately? State and local laws may prohibit this, but this may be an interim strategy.
In any case, part of the real, future value of the property, other than simply filling up vacant lots, might also revolve around the new owner (maybe that will be you) buying up cheap manufactured homes, placing them on the vacant lots, then renting both land and home. Rents won't quite match stick-built, but I know of a really large company in the space that does this quite successfully. "Yes Communities" is making money hand-over-fist doing this with over 12,000 units (my Wife works for them here in Denver). Anyway, I digress, but you might also consider buying units out of personal property tax liens for near pennies on the dollar, then moving them to your new park.
I wish you well!