How to calculate value add from RTI permits in Los Angeles?

[Braulio Hoyos]

I'm a real estate agent and have 2 investors who are ready to sell their investment properties (duplex & 12 units) and both have ready to issue permits with the city of Los Angeles (the duplex has RIT for 2 more units, and the 12 unit apt has RTI for 5 more units). I know how to comp the properties but how much value do RTI permits add to the property? The duplex client says $150K for the 2 extra units but I don't want to put it on the market and have it sit for a long time. Any advice is appreciated. Thank you!