Since you are new, it is not wise to invest alot of money into this thing until you know for sure it's what you want as a permanent side job, or full time Bondsman's job.
Basic equipment:
1) Threat level 3a BP vest. Galls has some on sale right now for about $400. You may find used ones on E-bay, Craigs list, pawn shops, cop shops, etc. but you don't want one that is less than 3 yrs old. And stay away from the ones that were made in China. They were recalled due to failures.
2) Restraints- 2 sets of CHAIN handcuffs..not HINGED....Why ? Because HINGED cuffs cause nerve damage to defendant's wrists. 2 sets of leg irons. Dog leash is good advice as well.
3) 2 "AA" Mini-mag light---not the heavy duty 3-4 D cell maglights...instant lawsuit.
4) The advice about training and mentoring is absolutely dead on. Any other tools you think about purchasing may require state mandated training or product mandated training..such as Tazers, chemical agents, firearms, etc. This applies to cuffs as well. If you have no prior LE or Military experience, then you may be required to take a class in the proper use and application of cuffing techniques.
5) Laptop computer
6) GPS Device
7) Old Army Poncho--these are fairly cheap at any surplus store. Multiple uses...if nothing else, as protection for your vehicles interior. I can't stand placing a filthy defendant in my clean car....
also can be used as a ground cloth for surveillance out in the woods, instant camouflage, rain gear, etc, etc. Don't forget the Febreeze either.
8 GSW Specific Trauma Kit- this is 1 of the most critical pieces of equipment a BEA overlooks. If you get shot out in the field, you have to know how to self-treat until help arrives. Esp. if you are way out in the country. You make these yourself. You can use any kind of bag, small backpack, etc. as the container. Duct tape, diapers, tampons, small bottle of peroxide, and blood clotters from Galls is basically all you need to plug holes with until help arrives. Again, these are fairly cheap to put together.
Duct tape has multiple uses....instant restraints, mouth restraints for spitters/biters (pillow cases work well too according to Scott M.), vehicle breakdowns, etc.
These are just some basics.