Legal Question

Not sure if this is the proper forum for this post so if any mod wants to move it to the right one. With that being said I have a question concerning a situation that may occur shortly.
The question is: If someone is a co-signer on a mortgage loan but does not live on the premises, do they have a say in who actually lives there besides the other person on the mortgage?
The reason I ask is that my wife had to cosign a mortgage loan for her mother to get a trailer to live in about 6 years ago, because her mother's credit was poor. Now she has just found out that her mother plans on allowing one of her other daughters to move in with her from out of state. This daughter, my wife's younger sister does not get along with anybody else in the family. When she was younger she made a lot of trouble for other family members with false accusations and other legal problems. She had been living out of state for the last 8 years or so an after her second marriage failed has decided to move back to the area. My wife does not want her to move in with their mother and we are trying to find out if we have any legal say in who can live there because she is technically part owner of the trailer. We are afraid, based on her past history, that my wife's sister could take advantage of her mother because she is elderly, handicapped, and living on a very fixed income.
I have tried to get my wife's name off the loan but keep running into roadblocks as her mother's credit score is low and that causes the payments to be higher than her current loan, and no other company wants to refinance it because she only owes $6900 and the trailer is 17 years old. Any advice or help would be appreciated on how to handle the situation above or how to legally get my wife's name off the loan as cosigner. ( I also tried to call the company who had the loan and asked that her name be removed. They said the only way they'd do that is to refinance it, but the amount isn't enough for them to do so.) I plan to call around to some lawyer's offices on Monday to see what we could do. Thank you.

From what I know of property/ real estate law (I do not claim to be an expert at all) I can tell you this:

First, laws vary from state to state so you should check the specifics for your state.

Second, unless you own the house under the classification of a rental property where your wife is listed as property manager, then she might not have much ground to stand on. Property managers or landlords have right to refuse housing to tenants based upon the sets of guidelines set by the state (and in some cases city) government. Since it sounds like the trailer was purchased as private property, then it is up to the discretion of those that own it who can live or be there. If no one wants her there, you could press trespassing charges on her. Or if she poses any conceivable threat to your wife or mother-in-law you could try to obtain a restraining order. Since your mother-in-law is a cosigner she has half of that decision making ability.

edit- You could see what the procedure would be for getting the trailer classified as a rental with your wife as property manager, but that would require her to have a license for that. Also it would change the amount of taxes paid on the property each year. But again, this depends on what state you live in.

murder your sister-in-law.

that's it, that's the only way.

i fought the law and the law won.

I saw something on Judge Joe Brown (it wasn't my choice to watch) where someone had co-signed a loan, and as a result was considered to have a "legitimate concern" about the property (not sure of the exact phrase, but something like that). Again, as has been said before, state laws can vary greatly, so look into local places that might be able to offer free or cheap legal advice in this matter.

I'd have to dig out my real estate book from college for this one. So as far as them having say in who can live there and who can't I'm not entirely sure. However, the co-signer, from my understanding, is liable for any damages, etc.