Here's a 3500# axle all set for electric brakes ($265):
http://www.amazon.com/Electric-Standard ... B001MXF18A It comes with spring seats that need to be welded on, no biggie, and it's a 5 X 4.5" bolt pattern, very common. Here's some 14" wheels that would fit th4e axle and your new tires ($39 each):
http://www.etrailer.com/Tires-and-Wheel ... 20352.html. So let's see, use the springs you have, no charge, parts for an axle all set with all the brake stuff and three wheels: $382. Someone might charge you 50 bucks to tack those spring seats on, and the parts for the 7 wire stuff aren't expensive really, it's the labor, maybe 100 bucks? I'm not sure as I do all this stuff myself. So maybe all together $500-600 for all new (and very common) stuff that will last for years. And really, in terms of rolling along, as long as the trailer is in good shape, that is all you would really need for many, many years of service. Take care of it and you're home free, or at least home very inexpensively.
I plan on doing something similar when I have the cash, i.e, just buy a new axle like the one above that's all set up with electric brake stuff, just needs the wiring harness. Actually I have the wiring harness now (it's cheap) and will be installing it so when I can afford brakes it's wired and ready.
I think you should keep the trailer and concentrate on getting a TV that would haul it. If you can't afford brakes right away, don't haul it far. Enjoy it, and don't fret so much. You own the trailer, and like any classic vehicle, it will require some investment over time. Be thankful it doesn't have a motor, transmission or differential! Just line out a plan for when you can get what and stay the course.
Frank
Tiny travel trailer - 1979 Sunline Sunspot. Tow vehicles: 2008 Subaru AWD Outback, 2009 GMC 4WD Canyon. For fun: 1923 T bucket hot rod, 1962 Power Cat tunnel hull speed boat. 1974 Dodge Dart waiting for renovation.