blasting all the rust and primer, fix suspect areas, full high build primer, one blocking, primer sealer, and a full one color paint (did you want the cage, interior and underside a different color?) is going to chew through your current budget.
Add lettering and clear coat plus buff, and you will be way over.

Roll cages are a pain to shoot, and the floor in and out will add too. I'd suggest a light color for those, so it stays cool and it is easy to spot leaks underneath.
The outside will not be straight with one blocking session, unless the guy is a master. Count on at least 2-3 prime + guide and full blocking to get it looking nice. Again, a light color is more forgiving to surface issues than a dark color. It will show gaps more.