As some have suggested, if you have a broader plan, a trailer isn't the end of the world. If the land is really good and you intend to stick build something in the very near future, then purchasing a property with a trailer could be to your benefit, simply due to the lower valuation of a trailer. In some cases a trailer isn't even considered an "improvement".
A few other problems to be aware of:
Energy costs will be significantly higher, easily double in the summer (triple with AC), and worse if your power supplier raises rates during peak usage times like they do here.
Health risks. Trailers are notorious for high noxious chemical content, such as formaldehyde, because everything is made so cheaply. Mold and mildew are more of a problem, both what you can see throughout the trailer and what you can't see, inside the walls. Mold is a serious health concern that shouldn't be taken lightly. If you have allergies or other sensitivities, trailers will exacerbate those issues.