However, you already gave him money that he spent and does not have to pay for the materials on your job.

I did a remodel on one of them when I first bought it - did everything myself - Home Depot quality materials - and did it for about $6k.

You need to know what you value in your current situation.Values such as: Price for quality in labor and material, or If holding costs are an issue perhaps duration to completion.As far as quality goes, do you want the 'Best of the Best'(out of your options) for your investment, or is mid-range quality OK.

Doesn't necessarily need to be something monetary but even the possibility of hiring them for your properties could be value.After a couple times of doing these, you'll have a better understanding of the process... but there will still be variables (labor, materials, your exit strategy also carries weight as well, whether you're going to fix-and-flip to a retail buyer or rent it out.)

The GC believes his costs will average around 30-33% of market value as his reasoning for pricing is 33% Material, 33% Labor, 33% Taxes.What is a reasonable % of equity you would offer a GC?

How high you can go up on such a small size parcel can make a big difference in returns.If the buildings are old the procedure to tear them down could get expensive.Also tenants on current leases the disruption to their businesses would likely need to do in stages more (start and stopping) with development and meanwhile labor and material costs can go up.

When I have previously checked into this with my accountant it seems their are very specific tests to pass to be considered a materially participating passive investor, namely that you must spend half of your time and at least 750 documented hours in passive real estate to qualify to deduct depreciation. 

The test is pretty tough if too much material is thrown at you!! 

. $2,000 in materials but we did all the work ourselves. 

I know price points when it comes to materials and vetting contractors and professional services3.