I'm wondering how this all went down without something unethical taking place...For your reference and anyone else's here, NAR Code of Ethics states:When an opinion of value is formed for a member of the public the opinion shall include the following:-identification of the subject property-date prepared-defined value or price-limiting conditions, including statements of purpose(s) and intended user(s)-any present or contemplated interest, including the possibility of representing the seller/landlord or buyers/tenants-basis for the opinion, including applicable market data-if the opinion is not an appraisal, a statement to that effect-disclosure of whether and when a physical inspection of the property's exterior was conducted-disclosure of whether and when a physical inspection of the property's interior was conducted-disclosure of whether the REALTOR® has any conflicts of interest (Amended 1/14)Also "REALTORS® shall be honest and truthful in their real estate communications and shall present a true picture in their advertising, marketing, and other representations."

Sponsors must have a pre-existing substantive relationship with investors for those deals. 506(b) deals cannot be publicly advertised.

Upon more research, I found IRS publication 523.

What is the best method for an early stage real estate tech startup to get real estate listing data (in the U.S.) in order to to apply it to software and make it public through a web marketplace where users can connect with the listings original listing agent?

The added benefit of this process is that you can also have your attorney sign the public records as "Nominee Trustee" before assigning yourself as the "Trustee" once the Trust has been established.

No one, other than you or the contractor, is responsible for the wall location problem.Most surveys do indicate easements recorded in the public records.  

Just that it is not the point of my warning below.Selling shares to members of the public is highly regulated by the SEC (in the USA) and by the state equivalent.

If I am taking pictures for marketing to the public, then I always ask the tenant's permission. 99% of the time they don't care.In your case, I would simply state, "I'm going to take some pictures for my records."

If you truly have a relative that left you a million dollars you probably would not be advertising this on a public forum.However I will “bite” and would advise you to get some estate planning going....

I would suggest you don’t make all that info public in this forum.