Giving you some leeway considering you aren't an engineer, the first thing you will learn about us is that we respond best to specific questions with specific answers. Your questions are way to general to get any kind of useful response here. You said your friend has been working on this for years. If there are some specific technical questions he has, we might be able to respond usefully to those. But asking for an overall general approach to the whole thing is way beyond the scope of any professional online forum.
I will however share my own opinion, as an engineer and a pilot. Many, many people have tried and to my knowledge none have ever succeeded in producing a practical steam powered lighter-than-air vehicle. The problem usually comes down to two issues: liquid water is pretty heavy, and the weight of the components required to contain steam and to convert its high pressure into useful work are also significant.