Twins: I have at least two indoor plants that are constantly propagating themselves - spider plants and purple heart plants. I'll put a subset of both outside for the summer but when the fall comes, I'll just let them die out there because I'm worried about bringing spider eggs and other bugs inside. So those plants will be free and I'll be able to grow new ones for the following year. The only cost will be potting soil.
I also have a tiny (12" high) norfolk pine that is barely hanging on. Not that the sun has come around, I see the needles are turning brown again so I'm guessing it is getting too much light. I'll put it in a shady corner on the balcony (there are lots of those!)
I'd like to try a mini herb garden on the dining balcony (chives, basil, oregano, for example.) It gets the most daylight and the previous tenant had plants out in the sunny corner (I could tell from the pot stains on the concrete.) I'm tempted to try a cherry tomato plant but am worried that I won't be around to water it in August so there isn't a point. I could move it to dd's but then she'll do the harvest not me, so there's really no point.
I'm tempted to spend $20 on a larger fir tree/bush of some sort. And another $20 - $30 on mixed flower arrangements in baskets (that I'd put on a stand.)
I need to find a cast-iron/aluminum stepped plant stand somewhere. The angel in the corner of the living balcony is a plant holder so she'll hold the purple heart since it is a hanging plant.