I've never heard of patent agents getting a percentage instead of a salary.
It also depends on how many applications are usually filed per month. One? Five?
What about other stuff, like responding to office actions?
I would want more details.
It's common. I work on percentage, as do agents in 5 other firms I'm aware of, including one large NYC boutique. It's not a bad arrangement, given that there are newbies willing to work for free in return for experience. It's a good way to get your foot in the door because the firm incurs less risk. The less productive you are, the less you get paid. No hassle about a pre-negotiated salary based on min billables (or billed), and a partner cracking the whip each month if you're not meeting your numbers. Especially in the first year it's not clear how much you will bill; takes that unknown off the table. You get a percentage of everything billed, regardless of whether it's a new app, or office action, or prior search, or whatever.
Remember, percentage is not salary. Firms like this deal because they don't need to keep cash around to pay you if work slows down. The down side for you is if work does slow down, the little work that does come in will be assigned to those on salary, since they get paid regardless of whether they have work to do or not. As I wrote above, what are your finances like? Do you have a working spouse or a couple of month's buffer in the bank? A major issue is *when* you get paid for work completed. There may be a month or two lag, depending on billing and pay cycles. For example, if you complete the work in late June, the bills get tallied in July, and you get paid in Aug. So your take home each month can fluctuate wildly. I've had month-to-month swings of 4X. As someone else suggested, try to get some minimum amount each month (even if it's a couple of K). But if you need a steady paycheck to pay the bills each month , you could run into problems. To get your foot in the door, you may have to accept this arrangement. After one yr (assuming you get good training ... again, clarify who will be doing that), you will be a lot more marketable and can renegotiate or split. But definitely get down in writing what the percentage is.
Also, the percentage is more likely a function of the firm, rather than the state. The big NYC IP boutique that I'm aware of gave 33% and that was to an agent with 3 yrs experience (he started at 30%). Even within a firm, the percentage is negotiable. Takes a lot of investment to train you the first year, they want you to stick around. Also I don't want to give the impression that all agents work on percentage. Others work on salary. But some associates work on percentage as well.