1 Parcel, 2 Buildings, 3 Units - How to determine ARV?

[Chad Eatinger]

I am looking at an off market deal in downtown Napa, CA for a double-wide lot that has 2 buildings and 3 units on it. The seller is a friend of a coworker who is looking to sell the property (it is 50-50 owned with a partner of his) and would prefer to do it unlisted to avoid commissions and such.

The problem I have is that I am not sure how to estimate the ARV of a non-standard property? 

The main house has been converted so that the upstairs is an 800sf 2-1, and the downstairs is a 900sf 2-2. A second building in the back is a 650sf 1-1. None of these units are currently rentable but I get a sense that once rehabbed the gross income on all 3 units could be close to 10K/month. The options I'm thinking are:

1) Renovate all 3 units and renting them out, hoping that I can run a BRRRR on the property and hold it or fix it, rent it out, and flip it.

2) Convert the 2 units (2-2, and 2-1) back into a single family residence, and renovate the 2nd back unit to get it rented. Not sure how to value this, but was thinking to use adjusted comps on the main house, and perhaps estimate a gross rent * area avg cap rate to add on a value to the back unit? How would you typically handle something like this?

The area seems to be very nice and updated (neighboring houses are running for approximately 900K-$1M for 3-2, fairly well renovated. It's also only a 10 minute or so walk to a very cute downtown napa, and is nestled in the heart of a small bed and breakfast area. The potential for a great deal is there, I'm just not exactly sure how to get to a good ARV in this instance? Any thoughts from the BP family? Thanks in advance!