Land Lover answers:
You are right on track by wanting to find the right fit. Some offices are very relaxed and some are highly charged, competitive environments - and everything in between. If you get your list narrowed to 3 or 4, make appointments to have an interview in the office. Ask to be shown around to get a feel for the office. Is there art on the walls or motivational posters? Take notice if the people are warm and welcoming or act like they'd trip their grandma to get the listing. Only you know what environment you will thrive in.
There are plenty of things you can spend money on, and it is important to have a clear picture of this up front. Ask about desk fees, transaction fees, franchise fees, who pays for advertising, business cards, signs, letterhead, postage, training, E&O insurance and web site fees.
Commercial is challenging, so you are going to need to know how you will be trained or mentored. Sometimes if you do this with a principal broker, there are minimal financial ramifications. But if you have to split commissions with an experienced broker for X number of transactions, that can add up.
Once you have taken a look at the offices and what they have to offer, compare apples to apples and make a great decision. People will tell you it does not matter which office you pick because you can change offices at a moment's notice and that is true, but it will cost you $$$ and clients each time you change, so choose well in the beginning.
Good luck to you!