Not "encryption". Since these are analog radios, about the best you'll be able to do is some voice inversion scrambling. Not very secure by any measure.
And licensing won't happen, unless you do it properly.
Radios that old are not going to be a good investment unless you have the time, money and equipment to maintain them. And even then, you'll be fighting an uphill battle.
Honestly, you are going about this the wrong way. Looking for "cheap" first, then adding requirements like encryption, coverage, etc. is going to turn out to be a not very cheap solution. Figuring out what your needs are should be your first step. Leave the e-Bay surfing until you figure out what you need. I've seen way too many people try and make systems this way, and I've never once seen it work. I have been in the position of trying to make butchered together systems work after the fact, and it gets expensive. It really is much cheaper to do it right the first time.