If you play a marginal game and say to yourself, what harm would one more do, you could keep going and going until you have a menagerie in there.

You may be actually causing harm.

Creating a false sense that someone posting online is not subject to harm does them an extreme disservice, and will likely get them in legal trouble should the worst case scenario actually come to fruition.I will note that I agreed with some of your more specific recommendations, but I whole heartedly disagree that this person does not need an attorney, or should not venture out to retain one. 

@Jd Martin had a valid point which is that if someone gets harmed on the property, they are going after the landlord.

There's no harm in it the way there might be for a home sale.

In Michigan, you can insert this clause in your Lease:ILLEGAL DRUG USE: Tenant must not violate, or knowingly allow another to violate, federal, state, or local laws regarding the use of controlled substances or the use of alcohol by minors in or around the premises. 

Liability insurance shall be in form, substance and amounts reasonably satisfactory to Broker, but not less than $500,000 (five hundred thousand dollars).

(i.e. bedbugs, illegal substance, etc) good luck. 

But as one of the OP mentioned if your intention is to subdivide this and you have all these neighbors close to you.. then you need to go into mediation mode and make sure you have them as allies and not enemies they can cause you far more harm in the land use process than simply bugging you about walking on your property.. the cost of perfect some silly  right to walk on your property is far more than anyone is going to spend in the real world unless your land locking them.

Being listed as an additional insured does absolutely zero harm to you, however it does protect you in the amount of the liability coverage on that policy and it also pays all legal fees up to the point when the limits have been paid out on the policy or the claim is denied.