I see that they charge a fee and you have to upload a lot of info about the property as well as personal financial info.

Personally, I have predicted too many crashes, and hence missed out on the booms when I was wrong.  

I own a three-family house in Queens, NY.   

I've owned a couple rental condos that I sold in years past, but I've never dealt with the sale of an apartment building so I'm pretty new to this. 

I also own properties in landlord-friendly states where there's no rent control, so I don't need to pay someone to leave in order to increase the rent.To address the other points in your post:This is why having a proper purchase and sale agreement is so important.

Don't be the person that you can see taking a cell phone photo in the bathroom mirror :) Most importantly, reply quickly when people reach out with interest.

I happen to own 25 properties as an investor.  

I personally would rather not have my name or company associated with a contract like that if I wasn't the end buyer. 

I am personally invested in @Chris Seveney's fund (and have invested a couple of times into it) if that says anything. 

Here are a few options you might consider:Home Equity Loan or HELOC: If you own another property with sufficient equity, you might be able to take out a home equity loan or a home equity line of credit (HELOC) to cover the $140K.