I have worked with several clients in a tax capacity who are involved in informal partnerships.

If there is no problem then the HELOC will provide more flexibility since the cash out re-fi may yield more proceeds after improvements when applying the 70 or 80% LTV limit whereas you might get improvement proceeds from an investment loan but you won't want to because there will be a lot of red tape, inspections, draws, lien waiver compliance and a lot of other crap they load onto improvement loans on investment property.

No need for a van load of guys to have to knock it out in a day.

This is a loaded question.

Plus it's hard to say without seeing your full debt load, but even if they are giving you 75% of each property to offset PITI for each property (if they're not on your Tax Returns), they still might not be calculating things correctly from what it sounds like.  

However, paying off the loan would reduce your debt load, simplify things for your family in the long run, and remove any restrictions the SBA loan may impose, particularly around building the new units.

If you have the capacity to change it every cleaning, I don't see an issue but I haven't had any issues with about a once per week draining so far.$150 per drain and refill seems a little high, but I am not in that market. 

I live in California but i am familiar with the area since i started my career there.That's a massively loaded question with no short/easy answer. 

As far as the content it’s loaded with gems.

Let's say $100/hour fully loaded, plus a truck, overhead and then add another 20% profit on the total (material and labor), because that's the whole point of running a business.