I can additionally recommend to allocate some basic features that you want to be present in your MVP and investigate how much do some app development companies charge for those. Usually, they can share rough estimations per fundamental app functionality in a form of hours required for app development, just like here - https://topdevs.org/blog/app-development-costs. Surely, each development company may calculate the development time differently and each has their own hourly rate, but you will have an approximate cost for your MVP.