Are you a good tenant (always pay your rent on time, maintain the value of the property, attract a clientele that is desirable to other businesses in the area)? If so, you have some power. No landlord wants to lose a good tenant. The only reasons a landlord would pitch a 30 percent increase are (a) you're NOT such a good tenant, (b) it's a hot piece of commercial property that is certain to rent quickly for that much or more if you leave, or (c) he is the kind of person who believes in "pitching high" to start the negotiating process.
Assuming it is (c), this was just his way of saying "I have to increase your rent." 30 percent was probably the highest amount he thought he could put out there without getting laughed at, and he expects you to negotiate from there.
Begin by reinforcing your power -- have him confirm that you are, in fact, a good tenant. Then let him know you really
want to stay, but you don't see how you can with a 30 percent increase (notice you didn't say you
can't or
won't, so you haven't backed yourself into a corner). Ask him what cost increases or other factors have caused him to need to raise the rent.
As he explains, put yourself in his shoes, listen carefully, and empathize -- after all, his taxes, assessments, insurance, and similar costs have likely risen, and gas and food is costing him more just like it is the rest of us. Try to calculate a reasonable counter-offer based on his responses -- for instance, if his cost of ownership has increased by 4 percent, maybe add in another 3.5 for cost-of-living and pitch the idea of a 7.5 percent ("How about a 7.5 percent increase? Would that get you what you need?").
He might accept, but he'll probably counter with something higher. Don't go up on your offer without getting something in return (for example, if he responds that he might be able to scrape by with just a 20 percent rent increase, you could counter by saying, "I could possibly handle 12 percent, but I'd want that front door replaced" (or a new sink, or new paint, or a longer lease term, or anything else reasonable that you'd like to have that he'd have to provide in order for you to agree to pay more). You'll probably go back and forth a few times like this until you have an agreement.
Before you start any of this, calculate your absolute
bottom line and be willing to walk away and find another space rather than exceed that amount. For example, if you calculate the cost of moving and decide your absolute bottom line is a 17 percent increase (i.e., it would be better to move than to pay more than that), and he insists on at least 20 percent, tell him: "I'm sorry, I just can't pay more than $X (17 percent)" and keep repeating it -- and stick to it (even if you end up having to move)!
A final tip: When you reach an agreement, make him feel good about it -- tell him he negotiated more from you than you expected to give (say that even if you would have been willing to pay more), but also tell him you appreciate the fact that he was willing to come down from the 30 percent and work with you so you could keep doing business in the same location. You want him to feel like the "winner" in the deal, and to feel like a good person, too. It will make all your future interactions with him easier.
Hope this helps. Best wishes. (Let us know how it turns out!)