If you are new to it, you may find .45 one-handed very frustrating. I waited almost a year to start, practiced exclusively with a .22. One reason was to master technique, the other was to wait until I got a reloading press.
Then the problem may come that you out-shoot a run of the mill .45 at 50 yards, and need a $2000 bulls eye 1911.
So I am 100% of the belief that your money would be better spend on a decent airgun that would let you practice on days you can't make it to the range. I'm of the belief the your 900 .22 leg scores should be about 810-820 before bothering with a .45. Put another way, you ought to occasionally see a 50yd. 90+, and most 25 yard timed and rapid fires should be about 95.
But hey...it feels good to shoot the big gun. Do what you gotta do!