ATP is kind of expensive. One of the benefits of going to ATP is that you get a lot of multi time, but that isn't so necessary anymore. Right now, any regional will take you with 25 hours of multi time. Only a couple years ago, the more desirable regionals were asking for 100-200 hours of multi.
Most local schools can get you finished in 6 months. I have seen guys finish that quickly and only spend 2/3rds the cost of ATP. Shop around and see what you can find.
Also, there are a lot of flight schools that are willing to pay for your CFI certificates if you commit to them. These schools are often located in Florida and Arizona. This can save you some money.
As a flight instructor, I was making $33/hr, and I saw some guys make $6000 net in a month if they really worked their butt off. Those are on good months and not all months are the same, obviously. Weather dependent...
Once you get to a regional, most of the regionals have raised first year pay. A few have not, and some of them have bonuses for new hires (so second year pay ends up being a pay cut). If you include per diem, there are FOs at my company making $45,000+ gross first year. Only Mesa is still paying $22 per hour. Many regionals have increased first year pay to $35+/hr.
At my company, we have plenty of extra flying available. On my days off (within the limitations of FAR 117), I often times pick up extra flying. We also have flying available at up to 150% pay. Some companies are offering extra flying at 200% pay. If you want, you could probably do some nursing shifts on your days off, but if you just want to fly, there are ways to make extra money.