Are you talking about spraying pastures? Row crops? Brush on rough terrain?
I'm not real familiar, what is the 5030, about 50 hp, maybe 4500 lb.? If so, anything over 100 gallons, especially on hilly/rough/uneven terrain, would be iffy.
Even with a 100 gallon sprayer (50 gallon for that matter) you want everything lashed down tight on the three pt. hitch. I mean very little, if any, side-to-side play. Imagine 100 gallons of water in a 150 gallon tank suddenly shifting to one side on a slope. I have had that happen when there was six or so inches of lateral play in the 3 pt. hitch. It can shift your "compass heading" a good 45 degrees if you don't have a lot of weight on the front end. One hundred gallons would be my max for that tractor.
One hundred to one hundred fifty acres is a lot to spray. If you calibrate your rig to spray 10 gallons per acre, that is ten to fifteen tanks of mix.
The fewer gallons per acre, the more critical the preciseness of calibration and application is. I usually calibrated for 20 gpa, I knew what size my fields were, and I could calibrate by guesswork. You can't get by with that on unfamilar ground, especially if you are applying somebody else's expensive chemical.
"Hey, you know that Roundup that was supposed to cover your 20 acre pasture? Well, I got about half way with it. You better go buy some more so I can finish for you."
As far as brands to look for, I would just suggest that you look at the over-all sturdiness, ease of extending booms, securing and bracing of booms, type of regulator and pump, etc. Go see what some of the bigger farmers are using.
If you are going to spray for neighbors and charge them for it, you probably need a commercial applicator's permit.