Or is it calculated daily and the base rent increases after 10 days when the late fee hits the account?

That sounds like a lot of work and I'm sure he would prefer to avoid that work and just sell it for $1.9m or $2.0m.if I were to buy it from him, to get to cash flow neutral I would need to increase rent on all 6 units to market rates and my monthly payment would need to be close to $6.2k/month, which would be $100k down payment, $1.7m loan with seller financing at 2% interest rate and flexible ballon payment.What would you do if you were me? 

Furthermore you can vastly increase your returns through leverage using a non-recourse loan but that will definitely trigger UBIT but again the numbers can still make a lot of sense. 

In California, this transfer could also trigger property tax reassessment, increasing the tax bill.

I think you're missing another point-- if rates increase.

Pricelabs has increased my occupancy and revenue significantly. 

Currently we are seeing STR owners posting for sale due to reduction in prices they can get per night and the vacancy rate increasing. 

They become renters, MASS increase of renters.

. $8k cash flow (this will increase over time because you are in an appreciation market). $6k principal pay down (based on your current loan). $20k appreciation (based on 3% which is conservative, 4-5% is the historical average).

. - In the event that you do get a deal, that you do not violate the intent or letter of an increasing number of anti-wholesaling laws, and that you actually receive an assignment fee, you will walk away thinking that your role is over.