Based on your post, I think you really mean that you are interested in travel nursing, not agency nursing. I recently started traveling and I like it. You have total control over where you work and the hours that you want to work because this is something you discuss with your recruiter beforehand. How much you earn depends on where you are working. Some states are notoriously low-paying, others pay better. But, don't be too quick to jump at any offer that seems to be paying a lot. Sometimes the hospitals pay higher because they have problems retaining staff for a variety of reasons. Even if such a facility is paying a lot of money, would you really want to work there? You should also consider that a higher per hour salary doesn't necessarily mean that you will end up with more money in your pocket at the end of the day. For example, some places pay very high hourly rates, but you may end up paying more state taxes than you are used to paying in your home state and the cost of living may also be much higher than it is in your home state. So you have to do the math.
You also have to be careful when agencies quote you rates. Most of the time, the advertised hourly pay is blended, which means it is not your straight pay but includes all your bonuses, OT, diffs, etc. Don't assume anything when you talk to a recruiter because I learned from experience that some of them won't tell you everything, and some will even flat out lie just to get you to sign the contract. Be sure to ask if the housing is free and private. Ask if they will pay your travel-related expenses or if it will be deducted from your pay. Ask if the position comes with a free rental car because most will expect you to pay for that. You also have to ask what type of per diem allowances and tax-free money you will get towards your living expenses if you decide to pay your own housing and travel costs. Just always keep in mind that the less they are paying you the more they are keeping for themselves. You are going to work hard for your money so you always want the best deal possible.
If you don't want to float, find out from the recruiter what the facility's policy is about travelers and floating. Some hospitals always float travelers first. If you don't want to float you have to get that in writing in the contract before you go. As for benefits, some travel companies offer better benefits than others, and it is not always free. You really have to shop around and go with the company that best suits what you are looking for.
Finally, I would recommend that before you sign any travel contract, read ALL of the language and, if you don't understand it, pay a legal aide or an attorney to look it over first. I came across one travel company with a contract that is nothing more than a set-up for the royal screw. Some of them have language in there that permits them to decrease your earned hourly pay and not pay you OT under certain circumstances (i.e. if you get sick or have some other type of emergency and are not able to work the the full number of contract hours for the week). A reputable company would offer you the flexibility to make up missed hours either during the contract period or at the end of the contract period. I've seen one contract that makes you liable to pay a hefty penalty fee and also permits them to pay you only the mimum wage for the last week that you actually worked if you terminate the assignment early for any reason. I personally would not sign any contract that doesn't have an escape clause, or one that requires me to pay the agency any penalty fees at all. Once your signature is on that contract it means you agree to whatever is in it so be careful.
Apart from all that technical stuff, I would encourage anyone who can to travel.