For the state of Michigan, the average land rent price according to these surveys was $127 per acre in 2019.
https://www.canr.msu.edu/news/farmland_rent_past_present_and_future
So based on those figures for your state you could charge them. $130*30 = $3,900.
Lets say you want to be nice and only charge them $3,000.
Cows tend to go for a price of $1 per pound.
https://www.napoleontack.com/marketrpt.htm
So you should be getting 3 cows per year, but that might be too much beef. And you would have to kill and package the cow yourself. But I do recommend that you price out your what they have to offer based on those metrics. Maybe you need some laborer to help build fences. Or you want some bee hives. Or just a consultation.
They do understand that you are a new owner and will probably ask for more
money to lease the pasture. So its okay to ask for more. You can ask the previous owner how much was traded for that 30acres. Maybe they can help you put in a fish pond, that will give you all the fish you need for decades. Or maybe they have some locally adapted cultivars of vegetables and fruiting shrubs/vines/trees that you would like to get from them.
Iterations are fine, we don't have to be perfect
My 2nd Location:Florida HardinessZone:10 AHS:10 GDD:8500 Rainfall:2in/mth winter, 8in/mth summer, Soil:Sand pH8 Flat