Apparently it does not contain too much sodium, although you probably have to apply sparingly (like any fertilizer). Most plants can (and must) tolerate some sodium in the soil. Some plants are much better at this than others. It would probably help if these balcony plants are getting rainwater or non-salty tap water (like, you don’t have a water softener).

Urine doesn’t have the same parasite issues as feces but probably best to skip using it if you had a UTI or were regularly taking medications. I’d also just apply it to the roots and not the whole plant (like any fertilizer). I don’t know, I’ve never used it, I just know it has been used historically and it has a ton of nitrogen. Anecdotally the spots in my (extremely rural) yard where I’ve pissed green up noticeably.

I mean… for the truly free solution you could potentially use your own urine. It’s a little much for most people but historically it was used.

Make sure there’s absolutely no wind. Those one-handed clamps and temporary lumber for bracing really come in really handy. You’ll probably also want to get the foundation totally complete first, so you can then get the structure all assembled in one day. A lot of metal structures are essentially membrane structures, which aren’t strong until they are complete, so you don’t want to leave it overnight partially complete.

Looking at the picture on the box, you’re really going to want some help, or a tractor with a loader, or something. It’s possible if you are supposed to assemble trusses and then lift them into place that will be really difficult by yourself.