Hi Kevin, move!
Just joking. You will need to compromise because of your situation. Hi Q antennae are your best bet. ISO loop/Magnetic loops are expensive, narrow banded, directional unless mounted horizontally. MFJ have a few good ones, but they also have a few good balcony antennae, MFJ 1622/1623/1624/1625. Just remember Hi Q antennae carry very hi voltages at the fee point and typically you are very close to it and in the radiation pattern.
MFJ also has a nice artificial ground MFJ 931, good to tune a random length of wire as a counterpoise and save you having to get different length counterpoises swapped in and out.
You can also look at a Buddipole/Bobbipole option, or even mobile antennae like the OPEK HVT-400B . You will need about 23 feet of balcony and it will be directional, but the OPK HVT-400 mobile antennae can be mounted on a clamp-on mount. It can be set up so you just need to move the jumper up and down the coil and tunes easily.
Other compromise antennae my be a slinky antenna. The apartment height will make up for the limitations and get you contacts.
There you have it. Just remember most things in HAM RADIO communications involves compromises. You are in an apartment. The only thing that will get you a flat SWR across the most of the bands, be reasonably priced, and work in most modes, will be a dummy-load.
Or, you can always go QRP transportable and set up nice QRP system with a full sized antennae in a nearby park or field.
Good luck and 73
de Ve3qth Robert