A tool that is very beneficial for design aspects of a business, if you don't have significant knowledge in design and don't have photoshop is indeed Canva.
On here you will find loads of templates to create simple and professional looking imagery, a potential to make an eye catching flyer or logo? It's great for creating imagery for social media too.
There are lots of free images on this site you can use, however some do require a $1 payment, although you can upload your own images too so potentially you don't have to pay.
You can't order your designs from Canva (maybe a future potential of the business?) but you can download it into a high quality image format, then find a company you can order these from. It may well work out cheaper than designing it on a website you order from.