About two or three years ago, I was in your same shoes - the AR15/22 looks too expensive, maybe I'll just go a 10/22 and build it into a trainer. So I bought a little 10/22, got a rail, had the barrel threaded, got some good Tactical Inc mags, and it was a nice little shooter/trainer for trigger time. Very reliable, and when I have standard velocity ammo and my suppressor it's very quiet.
But time has passed, and I realized what I really wanted was more trigger time on an AR to better simulate the M16/M4. So, here I am again. I bought complete little .22LR upper off Gunbroker, and loved it so much I started to want to shoot it suppressed but wasn't confident in the muzzle threads. So now I'm hoping to finish a 5.5" dedicated upper so I can shoot suppressed .22LR in my AR.
Moral of the story? Buy what you want, what you REALLY want. Even if you have to bid time until you can afford it, you'll be happier in the long run and save some $$$.