Another way to look at it is this:
If your brother has money that is doing nothing and it would be nice to have access to some of it, then think of solar as an annuity. You spend the money up front and buy the installation and then, every three months, the energy company gives you a FIT cash back that you can use like an income. You can spend that money or you can re-invest it. In our case, so far at least, we do the latter. In so doing we put some money back in the pot and get some interest upon it and we have it for an emergency.
Now, I may be over analysing this, it's the engineer in me. There are many sad individuals like me though on forums such as this... plenty of us get a kick of logging what we produce from the panels, mapping shadows, understanding the physics behind the technology and helping others who are considering making the leap. It's almost a hobby for sad gits like me!
Interestingly, and this is part down to PV and part down to a change in energy usage habits, our energy supplier sent us a report recently showing that our like for like electricity consumption is 30% lower in the past six months compared to the same period last year. Thanks to awareness and careful use of the new installation it is amazing how much can be saved. ÂŁ300 of savings without even considering the FIT payback, is pretty decent I think.
PV is not a get rich quick scheme and it certainly doesn't make sense if you are living on the breadline or if you intend to move within a few years. As a long term investment however, it is pretty safe and quite rewarding at a time when you may well need the money (when energy prices are even higher and you could be retired).
Be careful and don't simply buy the cheapest system though. A carefully planned and properly installed system will not only give a better income but will also enhance house value rather than reduce it. Kerb appeal has a huge sway when you come sell a house irrespective of FIT income.