Get a .22 first, then a .45 1911
I would suggest the Browning Buckmark in 5.5." These guns are great in every way-accuracy, reliability, ergonomics, cost and easy to work on. They also are configured just like a 1911, so they are the perfect training tool. With a couple mags, cleaning kit and 5000 rds, you will be into it for less than $500 OTD.
A quality 1911 will cost 3-5Xs as much just for the gun.
Once you are proficient with the .22, the transition to a sa .45 will be much easier, IMO.
Shooter429