Property maintenance can include painting, drywalling, floor work, plumbing, and mechanical repairs. Contractors and concierges will either charge their clients a flat rate for each job or by the hour ($/hr). In some cases, they may also charge for parts and materials. The invoice must include a description of each service rendered and the corresponding cost. Once the invoice has been delivered, the client will be expected to pay the full amount by the due date indicated on the form.