Try and get matched pairs. i.e. a 1911 and a 1911-22. They'll feel the same, and target/plinking with your 22 will go a long way towards muscle memory for the 1911 itself.
My first pistol was a 1911 from Sig Sauer. If I had it to do over, my first pistol would have been the same probably, but at least I would have known better. I should have gotten the 1911-22 first.
There should be a 22LR twin for the 1911, the CZ-75 and the Beretta 92. At least I seem to remember seeing those posted. There's a guy that shows up on here, don't remember who, that seems to collect those matched pairs.
Stay away from the Mosquito. I've heard oodles of bad things about them, and I'm given to understand Sig doesn't really make them, just put their name on them or something.
As for .45 ammo being expensive, go to Walmart. Federal 100 round value packs for about 30 bucks. The 50 round boxes are about 19.