In our line of work we sell two things:
- Our work (outright) and the rights to copyright it, OR
- The right to use the work (a license), and retain the copyright.
We use the first approach when it's unlikely that we can market the same work to other interested parties because of its uniqueness. We hand it off. The client can use it, or flush it down the toilet. We've been paid in a 1:1 ratio for our time vs the work product, and the client owns it. We assume no risk other than not being paid for our time.
We use the second approach when it's a lot more likely that we can market the same work to other interested parties. (Think of Itunes, or app stores, or even the 'old' music business). We are betting on spreading our production cost out over lots and lots of purchasers. If we can earn more than our production cost, that's great -- but just to break even is a great achievement. Often with this approach, we assume all the risk (in other words, work for free) and earn money only through licensing.
I don't think any client will be willing to pay you for full development cost AND licensing that you're going to offer to other parties as well (namely, the client's competitors).
You'll have to decide on whether this opportunity is your Sure Thing before you even think about a licensing approach, because you may end up losing your shirt in the process.