This is the mistake we all make...fintech needs one person that can do everything, SMH.
1. Get a developer to handle your backend,
2. Get a contract developer to handle your frontend, or better still get a template and deal with any blowback that might result from such.
At the end, either or both of you might be frustrated. I have seen this over and over again, if you have the idea, please send the money.
Don't be pennywise and pound foolish.