To review, TMI stands for Taxes, Maintenance and Insurance, and on a net lease it allows the landlord to recoup direct costs of ownership from the tenant.
Each year the costs are tallied and a new TMI charge is calculated.
Some landlords want to charge for management as well, and slide in a management charge, often reimbursing them for their own time and effort.
Court cases have been launched by tenants and sometime landlords have been denied management fees under the normal TMI wording.
If you want to charge management make sure it is specifically included in the lease language.