I'm not a lawyer, so this isn't legal advice. But...
There are a number of ways for setting up a "right of first refusal" on a property. And everything's negotiable. So, in any case, there isn't a "typical fee."
If one were setting it up as an option, which is a technique I'm familiar with, typically there'd be some sort of "consideration," which is usually a fee.
However, the value of the option, and thus the amount that the seller would ask for the option fee, could vary. Here are two scenarios: You find a property that is probably worth $100,000 today, in today's market, in its present condition. The owner is willing to sell it for $80,000.
Scenario One: You might want a short-term option, say 30 days, to tie the property up, then find someone else who'd like to buy it for $90,000. You might pay the owner $500 or $1,000 for a 30 day option. Remember: Everything's negotiable.
Scenario Two: You might want a long-term option, say 3 years. Your strategy, again, is to tie the property up and hope that in 3 years the value increases above $100,000. The owner knows that, too, and requires a larger option fee.
In either case, the option gives you the right to purchase the property...but not the obligation. Same as a right of first refusal would. You'd want the option to be assignable--that is, transferrable to another party. And the owner might seek a higher option fee in return for transferrability. Again, it's all negotiable.
Hope that helps.