I would recommend starting with a new kit if you haven't build that particular kit before or have little experience building. Also, you don't have to deal with someone elses problems or worry about the condition of the vehicle.
Main thing is you shop around for prices if you are going to do the online thing. I like ultimatehobbies as they have pretty good prices on things, especially if you call in. here is there website www.ultimatehobbies.com
and they have free shipping I believe on orders over $50 .
Not sure what you want in an ESC, I run the Tekin G-10 which was a steal when they had the refurbished units for $50. They do sell the G12IIIc for $60. A great racing ESC. Other ESCs that I like for say bashing and light racing would be the mc230CR or MC330CR. The MC230CR can take down to a 20 turn motor ( ran 19T on it and it was fine ) and the MC330CR I believe can do 13 turns. Both have 6V bec which means you have max power to your servos so you get more torque and faster transit times out of them. Also, they have reverse which can be locked out as well and they are tiny.
For radio, there are alot of different units out there that work well. If you can afford it, get one that is FM. I like the Airtronics MX3, great radio for the money.
For motors, if bashing, a 19T motor like the Reedy Quad Mag is a fun bash motor that is quite fast and some tracks have classes for them as well. They run a 19T buggy class in a city about 2 hrs from me that was quite popular. I like the Quad Mag so much I run it in my Academy SB 4wd buggy in the mod class when things get really bad or you can take advantage of a more powerful unit.
If you want a stock motor, the Trinity P2k2 would be the best for balance between RPM and torque, the Monster is more RPMish and the P2k is more torque based. Orion Core is another good torque choice.
Hope this info helps.