Maybe some detective work might help.

My name is Nieko, I am a brand new Bigger Pockets site member after being a long time surveyor of the youtube channel and listener of the podcasts, and have now decided to jump into the mix of things, I just wanted to start a discussion on peoples first real estate Acquisitions, see how they were feeling during the process, did you do a super detective method of knowing every little itsy-bitsy detail before you bought in?

Are there any tools/sensors that could help with mold detection that other investors have used ?

@Sarah BuchananHi Sarah,I’m a police detective (and investor) that may be able to offer some assistance.

NAR even has software to detect mls access used in more than one ip address. 

If anything is amiss you'll detect something soon enough.On duplexes; "the good news is that your tenant is right next door, the bad news is that your tenant is right next door." quote from all cash's brother, also a very experienced investor!

If we're referring to the same property be sure to get an inspector that can detect mold (could be a little higher in price). 

I have visited there homes often and cannot detect the first hint of smoke.

@Jorge AguirreMost gas leaks are not detectable, but are found during the course of the inspection.  

In my own house, if I detect a mouse, you place a trap with delicious peanut butter.