Your occupancy will (likely) be much lower in the shoulder season and non existent in the low season, except for maybe the holidays.  

The reasons that come to mind to me are poor rental history and/or planning on having occupants not on the lease.I think typically for a college town you will have a much higher vacancy rate - since demand is very low for 3 months. 

Be mindful that Dodd Frank applies if you sell to owner occupants.  

My 8 unit loft building I've been at 100% occupancy since purchasing it only two years ago, I've increased rents from 7K a month to 12K per month.

If an assumption of a vacancy rate is not met ( for instance in a year you have 100% occupancy?

Occupants should own the homes (and maintenance) and park just charge lot rent.Find the prevailing lot rent for this area.  

See if the area is heavily rented or if it's mostly owner occupants.

if you buy as a owner occupant, 20K converted to 5% down is about a 400K property with the seller paying closing costs.

After reading the Occupants from Hell thread, I would approach a situation like this with extreme caution.  

OK, last week I found a house that looked good, but was listed as " Non-Profit", so I could not bid.This week it goes to " Owner Occupant" so I could bid, ( as an Invester)but if somone that wanted to live in the house , bid lower ,would still get the house.Next week ,or so it should go to " any and all bids" if it were still avalable.and the highest bidder would get the house as long as the bid was high enough for them to accept it.