Is the $400/month for the land a rent/lease cost, or is it the monthly payment to buy it?
The trailer can be skirted to protect it from mildly below freezing weather.
Have you priced having water and a septic system put in? Can Mom afford it?
Living on the acre of land and growing your food would be a nice life style, but it's not going to put more than pennies in your pocket, it may not even make enough to pay for gas and car insurance. It's more of a retirement life style. You need something that's going to support you now and live this way later.
Bill