How do I comp vacant land for Muli-family (LA/Van Nuys)

[Arthur Fuller II]

I recently got a call from a woman who owns a vacant lot. a Lot that I thought was 7500 sq ft and zoned R1.5 - come to find out she actually combined the lot with the one next door and its 15k sq feet. She got approval for plans for a 5 unit apartment but for some reason (I don't think she was able to get the loan she wanted) she isn't going to go forward with the build.

I don't know how to run the numbers on this lot. and I don't know any developers who are doing apartments. My goal was to wholesale the lot. There are a few multi's that have sold in the area that give me an IDEA of a possible ARV but I don't know the build cost - permit costs and there aren't any vacant land comps that I can use to get an Idea of what to offer.

Any suggestions?