Marijuana beyond your lease saying no smoking, is a banned substance so there is evidence of criminal actions. 

Tread softly, sounds like he's not yet convicted of the most recent activity.This applicant would lose points in my screening due to having multiple criminal events and for the most recent being so recent.Additional occupants rather than new applicants are a different animal. 

Additionally without permits you will hit a wall if you try to sell some day.Do not leave it to a lazy contractor, apply for the permits as the home owner.Any contractor that advises not to apply for proper permits is unscrupulous and verging on criminal in nature.

Despite the rental history, I know my friend wouldn't be one that buy and hold investors would jump through hoops to rent to: he's tattooed up, has a criminal record,  and no proof of income (likely no evictions though!

It is probably cheaper than joining the apartment association and they would have the means to qualify a new tenant (credit, criminal, rental history, income) and ensure that the tenants are signing a lease that follows the laws in CA. 

We should never allow criminals to get off scott free.

Department of Justice's publication Frequently Asked Questions about Service Animals and the ADA which are relevant to your situation:Q: Are service-animals-in-training considered service animals under the ADA?

Credit check revealed excellent credit scores, but also an incredibly high debt-income ratio; otherwise, no delinquencies or criminal background.

IMO, what a lot of people miss out on these forums is that while (A) it's great to start investing early but (B) if you're taking anything like engineering, life sciences, finance, accounting in school you will be hard pressed to do justice to your studies while trying to be a full time property manager/holding a job. 

The criminals get inside computer systems and send real emails with real info but wrong instructions.