you may need 3 IPs in total. 2 for the two private nameservers and one for your own website or you can use the IP as your main shared IP for your clients.
But there is always one way or another a client can find out who you resell from if they are determined to find out. Only way to avoid this is to get a vps or a dedicated server. Then everything is yours.
The customer can still lookup ARIN to see who owns the IP block. Odds are high it is your reseller provider. (If not, then your reseller provider is not very large since they don't have their own IP allocation?)
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You can use a reseller account, but use your own NS and buy a block of IP by yourself, or else your reseller account's provider will be trackable by your client. I believe one small block of IP will not cost you more than $15/month