Yes, the vast majority of hotels will allow you to check in when you are 18. Some require you to be 21, though, so you might just want to call and check. They will be glad to tell you for sure.
there are quite a few sites that you can search that will likely show you great hotels at the best prices available. check out the website BookMe and you will be able to compare prices on all the reputable travel sites in just a couple minutes. it s very convenient and will save you a bunch of time and money. Also, make sure you buy them online... otherwise they charge much higher fees for phone orders. good luck.
Yes you have to be 18 or older. You also need a major credit card. Most hotels do not accept the bank issued debit card with logo.
yes usually some hotels require a drivers liscense though but you prolly already have that
usually motels are 18 and hotels require someone to be 21