This is a much more difficult proposition and you will most likely end up in or around DC. 

Is it reasonable to make this proposition to them?

With a 100% FREE & CLEAR property -  should have no difficulties getting approved - presuming you have current income to make payments.Don't get bogged down in Analysis Paralysis - but there are some positive changes coming in Texas HELOC (Proposition 2 on Texas Ballot - voting tomorrow) should give you ability to borrow more of your equity. 

Research Proposition 13 limits tax increases to 2% per year.

It's a complicated topic, but there are 2 major economic factors that make them a super risky proposition. 

It depends of course on the underlying power prices and the savings or lack thereof being generated as a cost of ownership proposition.

Investing in real estate is never a 100% money making proposition but in terms of ROI, real estate can provide some really high ROIs.

While this is an interesting proposition I am not entirely sure what to look for in the warehouse business, thus I wanted your input of what to look for.

The cost is $295 and if they don't reduce your taxes by more than $295, you get back the difference (i.e. there's 0 risk for hiring them and only upside).Seems like a win/win proposition and reviews online look solid.

There are some good opportunities to flip properties in Illinois, which is typically a better proposition than renting.