I've done this type of work before (porting Android to iOS, and porting iOS to Android), and it doesn't strike me as great for a subscription service - instead,

I've done this type of work before (porting Android to iOS, and porting iOS to Android), and it doesn't strike me as great for a subscription service - instead, just advertising that you are Android porting experts would probably be sufficient, if that's the market you want. I'm not sure what the difference is between paying your company $5k/month for a year, for this Android-app-as-a-service, vs just paying your company $5k/month for consulting services (and maybe locking that in as a minimum spend). On your end, you could end up losing a lot of money by not estimating the porting costs correctly, and quoting too low a rate. Personally, I find that straight-up porting projects aren't very interesting (as a software developer), so I tend to take on projects where the client needs both iOS and Android apps developed from scratch.