I was working a full-time job and pt personal training on the side while going. That was too much so mow I just full-time job it and go to school. Congrats on doing it in the first place.
Some tips are studying is the priority if you want good grades. You're going to have to put it before everything if you want those A's. You should since you'll probably be paying out of pocket like me.
3 classes at the most. You wont be able to devote enough time to anything more than that. Even 3 is stretching it. 2 suits well for a 9-5er. You can then take 2 classes in the summer for one or two of the summer semesters to make up the credits. Uconn here in Stamford has an intersession semester which is same class monday-friday 5:30-9:30 for 3 weeks straight. It really is intense. I did one, Financial Accounting, and it was rough with the full time job. I'm not gonna do that again. Got an A so I cant complain.
The gym motivation wont be there as much because your mind will definitly be drained from work then school then homework. It can be done though. I get to the gym 4 times a week or so still.
Rest is going to be a huge key also. You're gonna get run down doing work, school and gym so make sure you rest up. if you have a test the next day focus on that not your bench.
O yeah, the 18 year old girls will drive you bonkers! They sure as hell dont build them like they used to!