alright, let me start by saying i'm not a machanic. and i have not had to buy a bike yet. my first one was given to me. so keep that all in mind with what i have to say.
1st, those bikes (honda cb's, suzuki gs's, yahama seca's and kawasaki kz [as well as other equivalents]) are solid bikes. this one is in good shape and only has 4200 miles on it. so unless it was completely dogged and not taken care of for those 4200 miles i would say the engine is in good shape.
2nd, in buying a bike you have two choices.
--- get new. you shouldn't have an troubles and you have a warranty. but you also pay a lot more in insurance. then there's the whole - it's your first bike and you might drop it (money down the tubes) or that since you've never riden before you might decide you don't like it after a year and now you have to unload it and take a hit on it.
--- get used. insurance is much cheaper because you should only get liability (assuming you have health insurance). hopefully you have no payments. and if you get a "starter" bike you know that you won't have any problem unloading it later on because there are always starters looking for a starter bike. BUT, you will have to figure in some work for a used bike.
3rd, i think these bikes will continue to go up in value personally. so being that it's in good shape, if you got it fixed, rode it for a season or two and kept it up, i think you would be able to sell it for more than you bought it for.
with all of that i'll say... the guy who is giving me my bike once told me that carburator is french for leave it the heck alone. he has rebuilt a few bikes in his time and he HATES carbs. so i don't know that i would attempt carb work on my own for a first project.
if i were you i would do one of two things.
1 - find a local shop with a good reputation and give them a call. tell them what you know and ask for a worst case senario on the carbs and ask them how much it would cost. if the worst case would be $500.00 you have that to work with. hopefully it won't be the worst case

2 - assuming you have been going to church while in bible college i'm sure you have to have some sort of machanic in your church. or one of the members knows one. or there's someone who rides bikes or something. seek this person out and ask them to go with you to look at the bike and see if maybe they would even be willing to help you fix the carbs.
if i could get number 1 or 2 solid and could get the bike for 500ish, i would probably go with it. but before you pull the trigger, what for someone who knows what they're talking about to confirm what i just wrote
