The reason why rent is so high in DC, San Fransisco, NYC, Seattle is partly due to rent control, zoning restrictions, limited building permits as well as NIMBYISM.

I put the land under contract contingent on all approvals and permits.

I've found a property close to my old job that I'm going to return to, saving me a 30 minute commute time. also because I previously quit my job that I'm returning to, I have a nice savings that I withdrew from my retirement (7k).It's a 7 bedroom, 2.5 bath, with additional separated 3 bed, 1 bath aparment behind, all sitting on 12k lot with 3500sq ft living space between them. as far as I know it's been built in 1950, but I'm unclear right now what has been updated and permitted correctly.

I will need a permit for about half of the work being done on this house. 

Would probably need a permit with your county and have it inspected.

How much is it going to cost to re-tenant (property improvements, holding costs, taxes, potential rent concessions, TI allowances, permit fees, architect/engineering, etc.)?

This isn't much time for construction - especially if you first have to go through a permitting and rezoning effort which are time consuming but add little value (from a dollar perspective)2.

We are currently renting the property long term, but once the current tenants move out we will do further renovations to clean up the property and host it on AirBnB now that we have secured our conditional use permit.

Back Story:My parents have a 4 plex in California (purchased decades ago)One of tenants has stopped paying rent (stopped paying Dec 18)Unfortunately I found out their 4plex is really only permitted as a triplex but when they purchased it came as 4 units (they made no updates. it looks like the back unit had been divided by the previous owner into two units)The non paying tenant is going to sue stating he's in a unit that's not legal and wants all his rent back since 2015 (when he first moved it)Looking at all options it sounds like we're going to have to settle with him. 

He already has permits, build plans, cash needed ($400k cash reserve for monthly payments to the bank), etc.