Partner 1 may also contribute physically with rehabs, but minimally.Partner 2-No financial contribution, but has the most construction knowledge. 

Furthermore, you mention tax mitigation strategies so I'm going to assume that you and your husband are both contributing to a SEP IRA, etc.

You can also consider 20+ other real estate accountants contributing to this forum.

The partnership will be 50/50, with me actually contributing the needed capital.

I am here mostly to learn from the experiences of others, and if I get a chance to share my own, I contribute as well. 

or only start contributing those percentages once part of the 5k is spent?

Should one or more siblings not wish or be able to contribute equally at this time, what are the options?

When employees work for a company, the business is responsible for paying half of these tax costs.Ultimately, the tax code is designed to make people pay less if they contribute more to the economy.

You could also consider a Charitable Remainder Trust or a Monetized Installment Sale. 

PMs should have escrow accounts for contributions from and distributions to you.