If they were the right land/building ratio and made sense to do a cost seg/bonus depreciation, could I potentially offset my entire W2 salary?

Rates will be more volatile and going into a cycle of rate easing by the FED's these rates are set to drop soon which could cost you in interest earnings. 

At a minimum, if you want to shelter W2 income you need to know the IRS rules regarding passive activity losses and the exceptions, and also about the largest tax sheltering deduction, which is cost segregation and bonus depreciation.

This deal showcased our effective renovation strategy and commitment to delivering profitable outcomes.

He even mentioned a term "sellers concessions" that I guess has something to do with the seller helping out with the closing costs.

But sometimes free can cost you a bundle if you violate local laws, or don't include something that is required in your state.

Selling costs will consume about 50%.  

A Syndicated Proactive Product Solution converts your repeatable project design cost into a investment vehicle, not only puts you in control of the whole project delivery process but also brings you repeatable product royalty fees in any projects adopted  the same product in the future, even the projects belongs to other people. check this out on Linkedin: https://www.linkedin.com/posts/karl-dixon-2b964656_ace-king-...

A few of the crowdfunding sites have proven to be quite effective and efficient. 

If you've never built, I would never build anything as it will take 3x as long, cost 3x as much, and violate 3x as many city ordinances.