In fact, I don't blame your business model so much, I find it smart from a certain point of view and I wish to succeed in the first place so that everybody "wins".

If the exchange rate with fiat currencies stays the same for the next months, the fact is that 30 GH/s at $120 with mining starting today is an interesting opportunity and you may even break even by mid-February but 30 Gh/s at $120 with actual mining starting in two months is a whole different story. Difficulty might be around 5,000,000 at that time and profitability, half what it is today.

For me, the biggest issue with your offer is that there isn't any fixed length of contract.
I could still manage halved profitability if I know I'll be mining for a year, for example, but when I don't know how long it will last?

I understand it's all about risk/reward and that it's everybody's responsibility to carefully read and understand for themselves what your offer is about but I find this kind of thread useful because some people may just jump on your offer not informed about all that it entails.

Thank you for your answers anyway.