We've got a septic system. Drilled well out back for water. 500gal propane tank for the furnace. Primary heating is via electric.
Septic system probably needs emptying once every 3-4 years, and the cost is pretty insignificant.
The well has more than adequate flow rate, and for the first time ever I found water that "tastes nice". Means no water bills of course (but factoring in the cost of a new well every 25 years or so, it works out about half the price of typical main water bills)
Electric heating isn't so bad at all - it's all on a cheap-rate load-controlled tariff, which means it works out cheaper than heating by gas or oil anyway.
Propane furnace picks up the slack when the electric heating is off. I don't see how it's any different to mains gas; I think it's comparable in price. Only 'burden' is checking the tank periodically (usually once a month during heating season) to know when to re-order (delivery company gets upset if the tank runs completely empty)
Flat roof: we've got one on an extension (and the front porch). I suspect they need new material laying once in a while, but for it to be easy work. So long as the drainage is kept clear I don't think there's anything inherently wrong with them (although I admit to preferring a peaked roof just for the loft storage space it gives)
Anyway, not 'bad news' in those terms at all. Maybe you can get some form of grant to sort out the windows (and/or other energy-saving stuff).
Oh, I did have storage heaters in one house once - hated them. Always seemed to be no heat available when I actually wanted it.
cheers
Jules