Setup an attractive web site, try to look legit. Show pictures of people with a supposed role, Chief technical officer, Pool Operations, Computer Sciences, Social Media Management..., the more people your fake team the more you look legit.
Offer a 500+ days ROI service with a contractual clause to stop the service once unprofitable.
That's all
During these 500+ days, you can pay back your customers (about 1/500 each day) without difficulty, because the payouts are just a part of what the customers paid for hardware, you don't need to really mine. Of course, you need to find a way to stop or lower the payouts before reaching ROI.
From time to time, lower the payouts - this is legit because difficulty is getting higher - which make ROI increasing (600+, 700+ ...) and protect your business.
If difficulty doesn't increase for too long (unlikely), lower the payouts because the cost of maintenance is getting higher (electricity or whatever you can imagine).
Offer discounts to people recruting new customers for you (3% seems enough).
That's all, your business is ok for years. You don't need to prove anything, customers are happy with dust return. If suspicious customers ask for mining address or other proofs, just claim that for security concerns you can't disclose these informations.
This ponzi scheme can last years because of difficulty increasing (you will be able to close contracts once unprofitable), because very low return on investment and because of newcomers. About 1000 days per contract to find a way to close it or to make ROI longer and longer.
Don't be too greedy, this is a scam built to last.
