If you'd like to sell ongoing product support, maintenance, customer service, etc., you can add this to your project as a Service Package.

To set up Service Packages, go to Settings > Company > Service Packages, and click "+Add Package"  

You can then fill in the details of your support package and choose to price it as a percentage of the equipment price, labor price, total project price, or as a flat price. 

Then select your program term - whether you'd like to bill your client monthly, annually, or if this package covers 2 or 3 years of support. 

If you are setting up the price as a percentage, you can also choose to apply Smart Rounding. You can round to the nearest whole dollar, or set it to round no more than a certain percentage of the price, and it will round accordingly.

Finally, select whether you'd like this service package to be added to all projects by default, or if you'd like this to be protected so that only admin can edit it. Then just click Add.  

Once your Service Package is set up, you can add it to a project on the Project Overview page.