I saw the picture you posted of the trailer and imo I think you can find something in your price range already usable. Look thru craigs lists for all over the place. I am looking for a inexpensive GN so I am always scanning Craigslist between VA & FL. I see ton's of inexpensive BP's. Good luck, and sorry for the family drama. It's not worth it. Riding and spending time with your horses is to bring calm and peace into your lift.
I agree with the posters who have suggested to just buy your own trailer. I don't know what your budget is, but surely it would not be too expensive to buy an older one.
I got my first trailer for $500. It had a new floor. I painted it, had the wiring redone and got new tires on it. Most of which was paid for by loaning it to family members or friends on occasion.
Keep your head up family can be tough.
I just bought a used a bp 2 horse for less than 4k. All refurnished inside. Just get a dirt cheap trailer and you can fix up any way you like. They are going for as low as 100$$. You have a any choice really and then you don't have to worry about anything again :)