What do I need to do to ensure that we disclose all necessary information (i.e. re: repairs required, damages, that we are aware of) to buyers?

The BRRR strategy is much more cost efficient long-term than flips due to the tax savings.

What due dilligence do I need to ensure current tenants won't be a future problem?

These are not reasons that people rent STR... they might be reasons why people come into town for a few hours, but you need a reason that they stay for multiple days to keep your business efficient.

I need advice on structuring the partnership and ensuring that all investments are handled fairly and equally.

Would love to help and offer recommendations on what to look for with PM to ensure your investment is well taken care of.

What are the logical steps in which to do these activities most efficiently. 

On the flip side if you enjoy your job and are good at it, you will create a nice flow which will lead to you managing your real estate more efficiently.

Does anyone have experience with Corporate Accounting that would be willing to train us to ensure our system is set up properly?

They can ensure you and the Seller meet your contractual obligations.