Question
The basic idea is a review app for landlords and tenants.
The landlord or letting agency would have an account with all of there properties on and tenants would have personal accounts.
Both landlords and tenants would review each other and you could view peoples reviews on their profile. A new tenant could then see what experiences other tenants have had with their landlord and vice versa.
I'm also thinking of having a communication part of the app for a quick and easy way to communicate with your landlord and report any issues to them.
Answer
Create a mobile app prototype using Proto.io and have small group test it for you. If they think it’s a good idea develop a beta and launch through TestFlight and get more users. As you grow you can leverage the user base you currently have and start to look for funding to build the app fully. Hope this helps!