When I was done with the renovation and had the permits I just needed something to get it listed, my attention to detail was not great.

Industrial you have to pay special attention to any environmental contamination of the site and the POTENTIAL from the type of industrial tenant as some are low risk and some are very high risk.

What are the steps, and things I should pay attention to. 

Since you have cash, they will pay attention. 

Realtors usually won't pay attention to you until you are prequalified by a lender.If you do have the money and meet all the requirements to get a mortgage then I would just start looking for the property now, buy it and rent out all the units.

Also, don't pay attention to "comps" that have been advertised more than 3-4 weeks without success - they are obviously NOT a good benchmark.

HVAC units are the leading work order because they never get any attention until they break.

Rentals seem to require more sustained attention but at lower levels (I would hire a property manager). 3) Other real estate investment activities seem more foreign, but maybe I'll learn more here and have a change of heart.I've been a member on here for a bit but I haven't really been engaged at all.

One small thing that caught my attention @Andrew Carlson is that if the seller is flipping through his checkbook for expenses instead of pulling up a nice clean spreadsheet, you should think about what best-practices to learn from him and which to learn elsewhere.

Jones Paypal provides a card reader that you use with a cell phone to accept debit card payments.