I'll pretty much echo what has been said as being good choices. Get a regular 22 handgun. Worry about conversion units when you get older or 1911's that fit conversions units. They are too big to CCW anyway for most.
My personal favorite is the Ruger Mark II or Mark III with 5.5" Bull barrel; blue or stainless > your choice. It is a handgun that shoots accurately, is reliable, and is a great training handgun for the future. Even it you like revolvers, no reason not to have a 22 auto. The price is right.
If you want a revolver, I'd look at Smith Model 617. I prefer 6-round cylinder, but it is your choice. I feel that it is safer in 6-round, although Smith would not make a 10-round cylinder that is not safe.
With used 22 revolvers, stick with Smith (Model 17 or 18) or Colt (Officers Model Match, Trooper Mark III, Diamondback). Ruger's single actions are good, if you like single actions. So are Colt's. Ruger SP101 might be a consideration if you can find one in 22. It will never be a Colt or Smith, but lots of people like them.
There are a numbe of current autos on the market. I mention Ruger, but go with one that you like the best and then shoot shoot shoot. Great training and lots of fun especially if you have a group of friends who have 22 pistols and rifles to go plinking with out in the woods etc. Remember to be safe and insist your friends are safe too.