I'm sure that po box is stuffed full of threatening letters, bills, notices and the like.

No one knows what will cause it, but as Kathy Fettke (if you don't know who she is go and start listening to her podcast and look up her website STUFFED with brilliant people https://www.realwealthnetwork.com/learn/real-wealt...has said, "Bubbles don't slowly leak...they burst." 

I think a suitable analogy is electric cars, its the difference between ford coming out with an electric car that is basically a ford festiva with  bunch of batteries stuffed in the front seats and the gas fill spout converted for a 110v socket compared to a tesla which was designed from the ground up to function as a sleek electric vehicle that is sexy and beats all records.

should I invest In a direct mail campaign with yellowletterscomplete.com Or do it my self and spend hours stuffing letters by hand?

If its within the past 6 months then he is probably stuffing the property to make the numbers look good.

Looks OK from the vacancy numbers, but 12% is a bit high, and you need to be sure the owner hasn't stuffed the place with tenants on special deals.2) Is the value really there.

Given that they just did work to the building they might have given deals to tenants and stuffed them in there to sell.Why are the partners selling??

If you're doing some googleing/searching for a few answering services to compare and shop, I'd recommend searching for things like "web call handling" "website order entry services" "order entry answering services" the more specific you get the more likely you'll find what you're looking for and not a keyword stuffing, outsourced to wherever service.

That basically amounts to stuffing your money in your mattress, very poor investor advice but each to their own.

They are stuffed with useful information :)