The very cheapest way to go, as far as the radios, are any of the Midland or Cobra FRS/GMRS radios available at damn near anyplace... Walmart, Best Buy, etc.... they are very low output (FRS is no license required and limited to less than a watt of output) and their range is very limited, but fine for a jobsite. They're so cheap, it's frightening. They market them as 1 mile range, 2 mile range, etc. but that's all bullcrap. Six blocks on a good day.
If you need more range, then GMRS license is the way to go. $80 for 3 years.. maybe it's 5 years... I'll have to look at mine. They'll issue a callsign (mine is WQPM744) which technically you should use once in awhile, but nobody seems to bother and the FCC doesn't seem to get too excited about it. GMRS allows 50 watts output, and most of the handhelds are 5 watts output. This is what we use. We use mostly Baofeng dual-band handhelds, VHF/UHF ham radios that also have type acceptance for GMRS, Land Mobile Services, etc. They're about $35 to $45 each. We use a variety of VHF and UHF mobile rigs in the vehicles, house and shop... in the 25W to 75W range. We have our own GMRS repeater, so we get about 50 miles coverage on a good day, 25 miles when the weather/conditions aren't good. We also use the MURS frequencies (VHF) when the UHF coverage isn't great. Our mobile/base rigs are mostly Kenwood and Yaesu equipment.. one Icom radio in one of the trucks. I bought most of it used off of feeBay or at ham radio flea markets.