Hmm, That's an answer with a lot of depends. 1st, unless I were parking it somewhere long term every time, at least a month, 35' trailer is a bear to tow and won't fit in every campground.
If none of the systems work and i'm guessing they don't as he's unwilling to provide a means to test them.....fridge, stove, heat, ac, plumbing, etc you're essentially buying a huge cargo trailer. In which case, i'd rather just buy a cargo trailer and build it out to suit my needs. It's also a large area to heat and/or cool, so that will cost considerably more than a smaller trailer and that's an on going cost that will never go away.
It also leaks and has leaked, which means this thing needs a TON of work and may even be at the point it's beyond repair. Personally, i think you can find a better one, even with your budget of $1000. I wouldn't even want to guess how much in repairs it's going to need. If you can save up a few thousand more, you can buy a pretty nice trailer with everything working and no leaks.