Make sure with your lofts that your cost estimate for rehab and what the city or county wants for compliance are in the same ballpark.A building that old might have a ton of surprises such as illegal additions, grandfathered permitting but as soon as the use changes you have to bring up to code, knob and tube wiring, asbestos, galvanized pipes, lead based based, out dated electrical panel for today's demands, and on and on.Check what type of leases are in place downstairs NNN,gross,etc. and if the tenant has to disclose monthly sales and how strong the guarantee is on the lease.

You have a few extra disclosures to make when you buy and sell as an investor who is licensed but the stack of paperwork for real estate is thick already, so whats a few more pages to disclose that you are licensed, but acting as a principal (buyer or seller) and not as an agent in the deal. 

Before I took on this property I want to disclose that I am a contractor and all the renovation work was done by me and my crew.1.

It's a business, just disclose, treat every deal like u would hope someone would treat u or a family member.

If he can walk into a house, disclose he has no money nor intention to close, and they still want to sign, OK that is their choice.

You're not a structural engineer, and you can only assume a house listed for sale is going to be reasonably safe, unless otherwise disclosed.

As an agent you have requirements to disclose much more than the non-licensed investor.

Now technically the agent who is de facto representing the seller in this situation would have a fiduciary duty to disclose these conversations with the buyer to them to help them in the negotiation process, as they would be a sub-agent of the listing agent if there is no written agreement with the buyer.

You're responsible, it doesn't matter that this was disclosed after closing.

@DL Martin the sellers disclosed they had some "issues" with the boiler last year, but the boiler works.