Quite frankly, this could be a encyclopedic volume set, such are the many main and millions of minor yet sometimes significant things to consider.
But here’s my short list on general purpose radio equipment buying considerations which every potential purchase should have considered if you are not into setting fire to your money -
Know exactly what you want the radio to be capable of, know what’s necessary and what features really mean and on this level, become as armed and familiar with your target options as feasibly possible within your means.
Know in advance of looking at your local retailer/dealer/website or other online source, what you can legally use and what licenses are required as this will affect both your usage and any legal right you may have to use unfair and also (in some countries) whether possession whilst unlicensed (in the context you buy for listening and maybe to examine for research knowing that this may almost certainly destroy any TA/certification) may actually be a criminal offense unless you’re either possessing some document of exemption or a restricted permit.
It’s even possible in some places, Cuba was one I recall in the past, where anything in civilian possession beyond a simple broadcast receiver was an actionable offense, I don’t recall if it was civil or criminal but it was definitely actionable in a manner you didn’t want any part of. Given that Cuba was never the most oppressive nation, it was one of a few where you could get a lifetime of being at least on a subversive watchlist for unduly being in possession of two-way radio.
Notably, I got an insight into the then Cuba scenario from an ex-Cuban who had been there and bore the psychological scars etc.
So don’t think that possession is universally automatically legal because you’re only intending to use as a Rx or monitor - it can be an expensive mistake to assume freedom of speech and communication gives you immunity.
- Having established how you can safely buy and use under your nation’s legislation, and in possession of both insight into the systems and equipment out there, think again about what you really need , some systems are definitely fairly narrow in their intended use, some are barely more than intercoms, others are fairly comprehensive with networking as well as simple simplex operation, whether having digital only or analogue only or a dual mode system matters.
If you’re looking at short range kids walkie talkie range use, and simplicity, anything license-free or license-exempt is probably as far ‘pro’ and commercial grade as you need. Equally, mobile/base station/handheld, unless you need range greater than your locale, licensed free or license-exempt systems may be as far as you need look - there are ‘CB’ type systems on UHF and VHF you could be looking at and some come with half-decent (if legal) half-wave and colinear vertical antennas in the package, usually quarter wave or half wave is more common but there are legit colinear antennas you can buy provided you pair it with a system where radiated power (ERP) won’t exceed the limits imposed by license or L-free/L-exempt legislated usage.
The license not needed options mostly don’t allow for exchangeable/replaceable antennas , so in which case - chose your system carefully, ensure it’s band used and setup will be suited to your needs.
I’ve seen a few hundred milliwatts ERP on suitable antennas on best use modes for the conditions do hundreds of miles with the right antenna at VHF, but unless there’s a hugely unusual tropospheric ‘tunnel’ caused by weather conditions, license not needed systems aren’t likely to go beyond d 30 miles very best and uncommon case without repeater use/gateway use and that’s pretty much not in the legit use of most license not needed systems.
So, decide, regardless of which provider and system, do you need 30 miles or less, if so you’re looking at license not needed or lower licensed grade civilian ‘leisure’ market setups aka UHF/VHF ‘CB’ types of thinking you need your locale and adjacent county or town kind of extended range.
On DMR, locally, I can manage clear communication on the local repeater on a couple of watts ERP or less on a handheld, less cleanly on analogue FM, using the factory supplied antenna from indoors if needed (not strictly valid use of a repeater over here in the ham radio world mind), so if you’ve got LOS or can almost get LOS to where you want to transmit to, you don’t need to be running power or ‘putting on the big boots’ as CB users would say.
So, know what you need, chose based on that, know your systems, listen to any clearly qualified or experienced tips offered and most importantly if you’ll need service and support worth more than invisible ink on glass, find a reputable outlet to source from and really get to know how things work as far as you can without breaking the TA certification of your kit.
At this stage, I’ll hand this over to others to cover the more specific etc since I’m UK based and no expert on US/Canada FCC governed kit.