Some domains have bulk search, but you don't have to buy all. Many registrars offer bulk pricing, but what that means will vary. Some offer discounts with a minimum of funding of the account equal to the purchase of multiple domains, However, they can be purchased each once the account is funded. Most will start giving you discounts once you have enough domains with them, but you have to ask.
Yes. absolutely. Most reseller accounts probably don't even resell, they are just to get the discount.
Commission at sales sites varies between 10% and 20%, often with minimum charges. Read and study here to see what sells for what prices.
Most registrars don't charge fees to transfer (push) to another person. to transfer to another registrar, you normally just pay another years registration added to the current reg.
Registrar transfer means you are changing companies who you pay to manage your domain. DNS transfer means you are changing who's DNS servers you are using.
Push is normally free. Virtually all have push in some form or another. Some you just push to another account, others (like godaddy) you handle more like a transfer and enter who is getting the domain and they have to manage the new account creation and accepting the domain.
