I moved into an office almost a year ago and have no regrets. I got enough space that I can have three or four employees in this location but right now my staff is all remote. Couple of things I learned:
1) I'm much happier and so is my wife. It's nice to leave the house and my wife is very happy to have me out of the house. It does create that separation between work time and home time and has helped me mentally turn work off which is almost impossible for me.
2) I found it very hard to find less than 1000 ft unless I wanted to sublet. I didn't really want to sublet so I ended up with more space than I needed/wanted but it still worked within my budget. If you're not averse to subletting, it's not hard to find someone with an extra furnished office they need to rent out. I found a few smaller spaces but none really worked for me and none would have been much cheaper than where I ended up.
3) My 1000 ft. is still cheaper than the corporate office suite solutions in my area.
4) If you are going into an empty space, figure out what it will take to furnish it. I ended up getting a really good price on some nice ergonomic desks/cubes/chairs from a liquidator. For what I was planning to pay for one egonomic desk for myself, I got four desks, modular cube walls, nice erognomic chairs, and a small meeting table for my office. Of course now I'm stuck with four which hurts my mobility but I can sell all of these off on Craigs list for more than I paid for them. Find your local/regional office liquidators. (I tried to just buy two of the desks but he didn't really want to figure out how to break up the set/mess with setting it up for display so he just sold me everything he had in that set for what he was going to charge me for two. These guys will negotiate.)
5) Utilities/taxes can add up. I was able to keep the utilities low by using a hosted, pay-as-you-go voip service. I was able to drop phones on my employees desks and we can trasfer/conf call easily and it was a lot cheaper than trying to install a traditional phone system/buy traditional lines/trunks. Most months I'm paying less than I would for a single line/trunk, and my equipment cost was much lower.
6) I haven't started actively looking to sublet any of the space but it's something I've considered. If I can find some other tech entrepreneurs, I wouldn't be averse to it. I would start marketing the space at some of my networking events, so if you go to any networking events, you might ask other founders if they have any extra space you can rent. They may have space they'd rent but don't want to go through the hassle of renting it/aren't actively marketing it.