Or after I file unlawful detainer?

You discriminate against the wines that aren't a good fit.What you described, assuming Canadian laws are somewhat similar to US laws, appears however to be unlawful discrimination.

The penalty for non compliance can be as servere as losing the property backing your note, loss of 3 years principal and interest, or anything else a judge decides to punish with.  

MA law states "landlord who directly or indirectly interferes with the quiet enjoyment of any residential premises by the occupant... shall be punished by a fine of not less than twenty-five dollars nor more than three hundred dollars, or by imprisonment for not more than six months.

Only gluttons for punishment would purposely pursue D and F properties when they have better options.

That constitutes brokering without a license and in many states, can be punishable by fines or even jail.There are legal ways to wholesale and illegal ways to wholesale, many new wholesalers do it illegally and as such, the “legal hurdle” I referenced.Wholesalers will also tell you that they provide a valuable service, however, the argument to that is in order for them to have enough spread for both their end buyer and their wholesale fee, they must convince a seller to sell well below market value.

If you're a glutton for punishment, you can take her to small claims after the fact and attempt to collect unpaid rent. 

If you do not follow the terms of the “Notice to Pay Rent or Quit” we may then begin eviction proceedings against you and you will be charged with the crime of “Unlawful Detainer” if a judge upholds our claim.The amount of rent now due, as of today’s date _________________, is as follows:Current Month Late Fee _______________Current Month Rent _______________TOTAL DUE _______________

Third, your property insurance should have coverage for "unlawful sale" if you do end up on the wrong side of a judgement.

Without the other party being licensed, this advice would be considered brokering without a license in many states and punishable by major fines and even jail.So long as the finder who is a tenant in the building is not negotiating a purchase contract and only getting you in contact with the owner so that YOU may negotiate on your own behalf a contract, there is nothing illegal (to my knowledge - I’m not an attorney so check with yours in the state in which this would take place) by you paying for information.