How to Vet Commercial Tenants and what type of lease to use?

[Marshall Smith]

Needing help on best practices to vet commercial tenants and best leases to use. ( NN or NNN and why)

Info: 1 6000 sq/ft. building. Currently 3 commercial spaces for rent, 1 apartment. (will remodel 2 other commercial spaces, and build 2 new apartments. Totaling to 8000 sq/ft. 

Commercial spaces are approximately 1000 sq ft each, downtown, great location, high visibility, lots of shopping, barbers, salons, attorneys, etc in the area. (an attractive location for any small business) 

Currently 2 salons occupy 2 of 3 commercial spaces. Both Month to Month. But are paying well below market rent. 600 each. No taxes, no insurance, no building fees, current landlord pays all building repairs.