Question: I am looking for a way that I can develop an app cheaply for a very specific use. 
Specifically, I would like to create an game that can be played online between different phones. 

I have some coding and development experience, and I would like to make the app iOS compatible (initially... open to Android integration later on).
Is anyone aware of a way to make an app without paying $99+ a year to be deployed on the app store? I simply need to make it available to approximately 15 people, and am uninterested in making any money or widely distributing the app. 
Many of the target audience are in low-income areas of the world and have very limited access to computers, so a mobile application is likely my only option. 

Thanks in advance for any help! 

I have done research into Apple developer accounts, but it doesn't seem to fit my needs. I have also looked into making an Ad-Hoc account app, but can't find a lot of info on the feasibility of this.

Answer: 
One thing to consider is what are the game performance requirements? 

If it is a simple game, using a [Javascript game engine](https://github.com/bebraw/jswiki/wiki/Game-Engines) may be a better option as it can be hosted on a server (and viewed in a browser) to start with, and later bundled in a progressive web app with [PWA Builder](https://www.pwabuilder.com).
To developp on Android, it's free, you just pay if you want to publish the app on store. 

For ios, you can't do anything without creating a developper account, so pay $99.
You're always able to use a cross-platform langage (react native, flutter for ex.) but as soon as you want to deploy on real apple device, you'll need to pay.