Just need to stat under the occupancy limit.Also keep in mind basement needs to be livable square footage, ie have egress and proper ceiling height. 

Make sure to include proper disclaimers. 

I've filled out those little "Enter to Win" cards at the mall for a new car and had timeshare folks blow my phone up for the next 3 months.

So well within the 30 day trial period.However, they continue to bill my credit card for the service in spite of the confirmed cancellation.Has anyone else had any issues like this with them?

The tenant pays a monthly premium and keeps an active bank account and credit card on file.

However, with proper cash flowing properties, that would be well worth it in my opinion. 

Can anyone recommend software which would accept monthly payments (from me to seller) and create proper 1099 forms for tax purposes at year end? 

For us we all typically use 0% business credit cards to furnish the property which can amount to $40-$60k+ depending on how crazy you go. 

The merchant also failed to provide proof that the cancellation policy was properly disclosed to the cardholder."

When you do it, you show your cards, but new people don't knew because they are thirsting for help and will take it from literally anybody.