Save up for it? Put aside a couple hundred per month or whatever you can afford. I really can't think of anything else you can do besides maybe putting it on a credit card, though that might be really risky and you'd have to pay lots of interest. I personally didn't get Invisalign until I was 27 and could afford it on my own.
PS: the "home-made" invisalign sounds super sketchy, so I'd avoid that entirely.
Invisalign:
23/31 U (2/3 done!)
6/6 L refinements; Completed 15/15 L
Metal braces 10 years ago