I'm buying a condo that comes with a parking space I don't need, so I'm looking at leasing the space to someone in a unit that doesn't have a parking space. Any suggestions on a good way to determine an appropriate price?

Storage lot near me in the burbs charges $130/mo for an uncovered RV space. I'd say at least $65 a month for your space. I'd make sure to have a stipulation that it has to be a running passenger vehicle stored there so someone doesn't junk up your lot.

I got some more info after I posted - Apparently the space has a value of $20,000. At today's rates, that would be the equivalent to a chunk of about $130-$135 in a mortgage.

Any idea if there is any sort of standard or customary percentage or other calculation based of the value? Based on the value I don't think it would necessarily be unreasonable to ask $100/month, but I'm not super confident in that.

how big is the complex? have any other owners rented out spots?

My wife's place had a decently active secondary market for spaces. The price would vary based on location and they shopped them on the community message board.

39 total units. 6 of them do not have parking available to them. The unit next to the one I'm buying doesn't have a parking spot, went under contract the same day we did, and the buyer is interested in discussing a lease for the space.

Not sure where you are located, but if downtown, you can look at what the monthly contract rates are in garages close to you. Potentially add a little for convenience of being onsite instead of walking to different garage.

If it is valued at $20k, I'd try to at least charge $200 a month or 1%

Ask your realtor if they have any experience in this, if not, see if there are any comps in the development.

Mathematically you can apply a cap rate to the value. Super janky but say take 7% of the $20,000 value = $1,400 annually or roughly $120/month.