Welcome aboard to Bigger Pockets @Leon Henry , very engaging first post.

Here is the key language (in my opinion) (found under the heading "Doing Business in California"):California defines doing business as "actively engaging in any transaction for the purpose of financial or pecuniary gain or profit" . . .

If your not a busy professional and can engage often they can be managed. the lower end properties in my mind are the play ground for the local landlord that does it for a living.Most of the bigger turn key guys will agree  Mike D a  Chris Clothier etc.. they will be the first to tell you buying low end high touch hard to manage properties are tough for those looking for what your looking for, which is complete passivity.

How ofter you engage the attorney just depends on how big or small the property is and where your ROI lands.

As for promissory notes, etc, you might engage the help of an attorney if you're not versed in this.  

Some of your suppliers would normally be engaging in what we call the "Spring Buy", which is basically an offering of discounted wood (PT, decking, untreated, etc) that the dealers take advantage of to stock up for the spring/summer.

J Scott timely book   I think from my personal experience in 08 when i was fully engaged in RE.. one of the biggest contributors that fed on itself was the fact that credit froze. 

This is why I got engaged to a realtor!!!!

Thanks for engaging my post!

Yes engaging in almost any activity for profit will be considered running a business by the IRS.