Does the balcony have a railing? If so, tie a couple poles to the railing, and run some type trellis between them. I recommend tying first, since that would be easily removed... but if possible, bolt or clamp the poles for greater strength. Likewise, if there is a place above where you could screw in a couple plant hooks, you could run string from there to the railing. You probably want check with your condo association to see what they would allow. I would think that if you choose attractive materials (such as a lattice trellis) they shouldn't have a problem with it.

Runner beans have a single stem which twines. They don't produce tendrils. Hence you only need one single vertical support per plant. With a lone bean plant one cane or string would be sufficient. It needs to be at least 6 foot tall. In the ground they will get to 8 feet easily but in a pot it might be restricted a bit. If you want to keep them flowering you will need to pick the beans regularly. Eat them young to avoid tough stringy beans. Feed and water amply.