Wow. Guess I have some questions to answer. I'm going to do this all kind of quickly as I'm kind of in a rush, but if you need clarification or another question ask away.
Vrogy: The best sniper for under 100 is going to be the UTG snipers, but you're going to need a scope which is going to cost you up to 60 dollars more.
For pistols, go for a nonblowback gas pistol, they can cost around 40 dollars each.
www.shortyusa.com has the NBBs and the snipers.
I don't reccomend a sniper clone like the "warrior" and "BE" but yeah, UTG I reccomend, but don't expect it to be the best, it is a 100$ sniper. People I know like it but I can't fully vouch for it. Although my friend had one of the older models and that worked quite well.
Panton: The M15a4 is an m4, it's just called that because of issues with trademarks and what not. Basically, Classic army couldn't get the rights to use M4.
A gun can never really break and be unuseable unless you completely kill it. Parts will wear out over time, but you can buy new parts if you know what you're doing. If you don't, take it in to someone who does. If it won't fire or its something internal, you can buy a new gearbox as well. If its external you can buy new parts like a new barrel, if you managed to break a metal barrel.
If you don't want to mess with replacing the gearbox and stuff, you can sell the parts and make money for a new gun. You can make probably more than half of the guns original value by parting it out.
Kraken: Haha, didn't notice you answered the breakdown question, thanks! I'm just leaving mine up as I'm lazy.
For anyone's concern I think we should list a mass list of retailers and give maybe a rating on each one out of 3. (3 Being the best)
I'll just list a couple to start it.
www.airsoftgi.com--US Retailer--3 Stars
www.shortyusa.com--US Retailer--2.5 Stars
www.airsoftatlanta.com--US Retailer--3 Stars
www.airsplat.com--US Retailer--1.5 Stars
www.redwolfairsoft.com--Overseas Retailer--3 Stars
www.uncompany.com--Overseas Retailer--3 Stars
www.wgcshop.com--Overseas Retailer--3 Stars
www.evike.com--US Retailer-- 0 Star
If you have a different rating, I'll make a basic average of them all and update it.
If you have stories about a retailer, tell that as well.
I'll also put this list on the first post when more come.
P.s. If you want me to do some gear websites I can also post some of that. I'm not sure we have any geardos in here but yea.
A couple being
www.tacticaltailor.com
www.optactical.com
www.blackhawk.com
www.triadtactical.com
www.botactactical.com