There are 2 ways to sell your products on mobile.
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1st way: User can make the payment for each product via Paypal or Credit Card.
In this way, the user must put his payment account information to buy each product. I think to decrease user's loyalty with this way, because they has troublesome to buy your product.
2nd way: User can make the payment for each product by his APP points.
In this way, user have to buy the points at least one.
These points are credited to user account and the total determines which level user qualify for.
After the user make first purchase, regardless of the amount, user will automatically be qualified for at least the lowest level, if not higher, depending on user purchase amount. Each tier earns a special discount on future purchases, and the savings only increase as the user increase the user's status.
In the user account, he will also find a special referral code for to him to share with his friends and family members. The code will provide his friends and family a scaled discount on their purchase,
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I am an experienced developer in web service.
Your project makes me interested as I am full confident that I can accomplish it on time with the best quality.
Looking forward to discuss further. Thanks.