The property is a 3 bedroom, 2.5 bathroom townhouse. 

Storm sewer, storm pond, sewer lines, water access, fire hydrants, public bathrooms, surface coverage, sidewalk or bike paths, setbacks, power lines and right of ways known and unknown, road access, etc.              5.  

We get various brands when they are on sale. 1oz soaps and shampoos and put out 2 of each in each bathroom.

You still have flooring, cabinets, bathrooms, plumbing, insulation, paint, etc, so all that cost remains the same it would seem. 

I redid the master bathroom by removing the tub and putting in a standing shower with white granite looking tile, and a custom glass shower door.

Newer appliances, free nice laundry, 2nd floor, yard space, storage, clean bathroom, included heat, installed window A/C.Appraisal suggested the unit was worth 2,300 a month, which I felt was a bit high, so I listed it for $2,150 with no move in fee and a 2k deposit.

.- Get a list of active properties in a zipcode with filters (number of bedrooms, bathrooms, price etc)

At least that way you'll get a pretty good idea on whether the original valuation is accurate or not.As for what to *do* with the valuation: @Rui Dias Costa took the words out of my mouth :)Sidenote: Are there any chances to add a significant amount of value to the property (e.g. another bathroom/bedroom)?

You can look at a mobile home and see it as an easy rental with new carpet, trim and some paint but there are other bigger uglier expenses that can come up.Roof Replacement, soft floors (water damage) in kitchens and bathrooms- most floors are particle board, exterior door replacement (special order), underbelly insulation falling, bad hot water tanks with rotten floor underneath (real joy), bad windows (water again), bad bloated siding (water), water damaged base frame around perimeter of home, cracked tubs (special orders) and frozen pipes (Good luck finding a plumber to come work on a mobile home- they do not exist). 

Unlike a kitchen or bathroom renovation your literally building a second house on the property and your dealing with everything from grading, soils, foundation, electrical, plumbing, framing etc.