Like any other hobby, you need to figure out how it will be likely used then decide from there. If you're going to be out coinshooting parks there's great machines, if you're going to be hitting the beach there's other sugestions, gold- that's a whole nother machine.
If coin and relic hunting, there are some great machines from Fisher, Garrett, Whites, Tessoro,to name a few. Also, consider the cost of support gear like recovery tools (digging tools), pinpointer, head phones, different sized/purpose coils.
If beach/water hunting, there are some great machines from Fisher, Garrett, whites, Tessoro...
If prospecting there are great machines from.....
You get the picture, lol. Most companies make machines to cover all bases. Check out Kellyco online for various options and kits. Some of the more popular starter machines are the Fisher F2 and Garrett Ace 250. Not less capable, but great bang for the buck. Also, the ground type where you will be hunting can narow your search a little bit.
HTH
-Xander