Free Persona Starter Kit
Personas are ficticious representations of your user demographics you use to build your entire business off of. As such, it's about the last place you want to assume anything and the first place you can help reduce risk.
As with any validation method, you have to start with a hypothetical. Simply take an educated guess as to who your users are. These will be your hypothetical personas. Now you need qualitative (the why) and the quanitative (who) data to back it up. To get you started, below are links to templates and guides to help you through this process.
Should you need a little extra help, I'm currently accepting and availble for any consulting work you may need. Reach out if you'd like the extra guidance!