Before worrying about developing the app or patenting anything, tell him to do thorough market research. How many customers are out there? How much would they be willing to pay for this product? What is different about this product (i.e. what product does it solve that isn’t currently being solved by existing products)? How is he going to reach these customers and what will be the cost of acquiring new ones? A little diligence up front is well worth the time.
Assuming he gets satisfactory answers to all of the above questions, he needs to think about how to build out a software organization. Freelancers on Upwork may be good enough to get you through the wireframe phase but it’s highly unlikely that you’ll get anything robust enough that you can charge for it. Even simple apps require a ton of development resources so he either needs to learn to code it himself (which is a full time job) and/or find developers willing to dedicate significant time to it. This likely involves giving them salary and equity.
TLDR: it’s a lot harder than you think.