I think most of the citrus trees don't reliably begin producing until their 3rd or 4th year. Dwarf bananas can take like 4 or 5. I've read that if you get fruit in the first season that you should clip it off so that you don't stress the young plant.

I am hesitant to drop forty to seventy bucks on a plant if I don't think I could keep it alive! Where have people gotten their trees? What are some reliable retailers? How much light do they require? I live in Philadelphia, so they'd probably only get to be outside from May through late September... would that be enough?

Here is a conversation about growing trees in containers. Filled to the brim with great information.

They want full sun. It's totally doable. This probably isn't a beginning gardener thing, but fine for anyone with some experience under their belt.

We're growing an Improved Meyer Lemon and a Key Lime. They are in large containers with high water and air holding capacity mix - they want good drainage. The Key Lime has really spiky thorns. They are heavy feeders, so they definitely enjoy frequent/high fertilization. The Improved Meyer Lemon's flowers have a wonderful scent. It does take a couple of years to get production started. We haven't had tons of fruit or anything, but our trees haven't put into optimal conditions until quite recently, and now we're looking to have quite the bumper key lime crop (for a still young/small tree). The Meyer Lemons we've had are delicious, very unusual flavor.

We found ours at nurseries out in the middle of nowhere - you'll get a MUCH better price that way. Hope this helps.