How much more rent would you charge a couple vs individual?

[Kendra Mattson]

I have a room in a house listed for $700, but I've had a couple inquire about it. I know rent should be more for a couple than individual, but haven't rented a single room to a couple before, so I wasn't sure what to tell them. I picked $875 pretty much out of the air and they said that would be fine, but thinking about it now an additional $175/mo for another person seems low. What is your normal "markup" for an additional person, if you rent to couples at all? For reference, the house is in San Diego.

Thanks!