I would like to have a spare wheel to use on my trainer so i don't have to change tires all the time. I'm trying to spend as little as possible. These are two wheels I'm looking at right now:
https://cgi.ebay.ca/ws/eBayISAPI.dll?...=STRK:MEWAX:IT
and
https://cgi.ebay.ca/ws/eBayISAPI.dll?...=STRK:MEWAX:IT
What I need help with is finding a casette that will fit either of these wheels.
Right now I have Shimano 105 10-speed.
Thanks in advance for your help!

Assuming your trainer has adjustments for resistance, you don't really need a 10 speed cassette. Pretty much any cassette will work as you just need to get the chain to line up with a cog.

So wheels are not made specifically for 8, 9 or 10 speed casettes?

most wheels these days are 8,9,10 spd compatible.

The first auction on the Ritchey is for the rim only.....its not a full wheel.

Thank you for pointing that out..
One more question, I have 10 speeds right now, if I put a 9 speed cassette will my shifters still work?

Check with your LBS about which version of 105 you have on your bike. the 2011 105 uses an asymmetrical chain that may or may not be compatible with some cassettes. I think it should work with a 2200 casette but I'd check to make sure.

https://bike.shimano.com/publish/cont...ty%20Chart.pdf

look at the chart that says "Compatibility: Rear Drive - Road" If I'm reading this correctly it means that you can use a Tiagra or Sora cassette with a 105 RD but not 2200.

Yes, the RD is compatible, but that doesn't mean it will work with a 10 speed shifter. The indexing is different. The throw from gear to gear on a 10 spd cassette would most likely be narrower than on a 9 speed.

Just scour ebay for a 10 speed cassette.

I'm going to the bike show today here in Toronto, hopefully I can find a wheel and a cassette.

That's what I would do.

Continental has a trainer tire, it holds up better than road tires,
when on the trainer, they say.

I got a Shimano 105 5700 cassette at the bike show for $62 CAD + tax. All I need now is a wheel.
I saw a set of Bontrager SSR wheels (exactly what I have now on my bike) for $150 but I only need the rear one.

fietsbob: that's what I'm using right now on the trainer.

A damaged wheel may also work for this purpose. A friend of mine put a massive warp in his rear wheel that was impossible to re-true. I sold him an almost new wheel that I had in stock and kept his warped wheel. I've now been able to get it straight enough to use on my trainer bike (the uneven spoke tension and persisting out of trueness means that I would never use it on the road). Ask around and see if anyone has a wheel like this that they could donate to you.

As said above, most modern wheels work with 8, 9, or 10 speed cassettes.

I got a used wheel from a LBS. It is untrue and the resistance unit (roller+flywheel) moves back and forth quite a bit
trying to follow the tire. Is this likely to cause any problems? The rim looks damaged so I don't think it can be re-trued.

I'm not sure what you mean when you say "the resistance unit (roller+flywheel) moves back and forth quite a bit trying to follow the tire" You might be talking about the cassette wobbling, which could be caused by a bent axle, which could be replaced (but the rest of the hub kept) but it's really hard to diagnose the problem from that description. More details and/or photos/videos are needed.