We plan to meet this week and i want to verify which contracts i need to close this deal. would i need (both) purchase and sales agreement / assignment contract?

AirBNB just verifies they upload anything even a fake ID they don't do anything else.

I am not an expert by any means,  but I do have rentals in south seattle and burien; near renton and I have looked into this a couple times when I had sec8 recipients inquiring about vacancies.The way that the housing authorities require you to verify income is that you can only verify income against the tenant's portion of the overall housing payment.  

Do a parcel search to verify.

So if anyone can verify that they are actually possible that would be helpful.

I want to minimize my ties/ hide most of my identity; so that if someone tries to sue or take my property they don't get everything and might not know what I own or may own...I want to know the best way to secure the land to keep people from dumping on it or living on it... the land right now is pretty worthless and I doubt someone currently would want to live long term there, but in the future amenities and with more people might move back/into the area, which currently right now is pretty darn rural and uninhabited. also, how would I find out if septic is still good since there were no issues before the structure(s) left or no longer stand...?

Even though you're planning to self-manage, I suggest you verify the rules for a state of interest! 

Scott shall not be considered active under the following circumstances: unemployed while seeking gainful employment, on disability from full time employment, retired from government employment, or other circumstances out of control and atypical to choosing to pursue his housing business endeavors as his sole source of primary income. 1.Should Scott choose to “actively” engage in housing as his source of employment as defined above, Scott agrees to give 25% (twenty five percent) of his net profits accrued from his active efforts during the period of marriage to wife in the case of a divorce.2.Payment of such percentage of funds shall be payable over 120 equal monthly payments, or equivalent to no greater than 10% of Scott’s New York State Adjusted Gross Income, verified annually with payments adjusted the 1st of November each year, whichever is less, to ensure no undue hardship to Scott or the business will be endured.

But, if audited, it will be very difficult to defend.The correct procedure is to get the contractor's SSN (have him complete Form W9 and verify against his SS card) and warn him that he will have to pay taxes on everything he was paid in 2018, including cash already paid to him.

(yes I spelled it like I got asked) My reply to them was that they do not make 3x the stated need of verifiable income if you need "housin" thus you did not even read my rules for application.