We are planning to develop one custom App per year for our customers on business partnership basis where our role will be App development and support. But we are looking for reliable as well as good business strategy firm or individual. What is best platform to find them or advertise our service ?
If I understood correctly, you are planning to create the app for free in exchange for percentages/shares in the business/startup?
If so, the best option would be to partner with accelerators/incubators and other organizations that work with startups who have good ideas. I personally work with hundreds of startup each year, so if you're interested, we can talk and possibly collaborate.