Debbie,
You will be basically subdividing your lot for the singlewide. This will of course decrease the value of your home. If you place a mobile home on the new parcel then you will have additional value there, but a singlewide will not appreciate in value like a regular home. So the added value you gain will not hold. If you want a market value study done just drop me a line I would be happy to help.

Larry Story
Coldwell Banker Triad
larry.story@coldwellbanker.com

not sure if that is an improvement in the property.
and improvements increase your taxes.
as for the value, like the price, it probably doesn't change it much

anyways

good luck