I can answer 2 - No. The actual registrar will keep the major portion of the fee and you'll get a percentage as commission. how much varies by registrar. But even registrars don't get to keep the whole registration fee when they sell the domain - they have to pay the wholesale fee to the actual registration board.
You "pre buy" a pack of domain name "tickets" ..at about $7.60c ( plus taxes ) or so The minimum is around 10 .. You resell for say $7.99 each ..so you keep actually about $0.35c per domain name sold ..the rest goes to the registrar who pays ICANN around $6.80 or so ..( plus tax )... ( the exact figures escape me )..but the principal is ..you aint gonna get rich on selling domain names ..( unless you charge more )..and your customers will compare prices ..so thats very very hard to do ..
Owning your customers names ( as in selling them a package ) or encouraging your hosting customers to let you register the domains in your name is the way to bad feelings , and lawsuits ..and if you are hesitant over $75.000.oo you might want to know that just few ( maybe even just one or two ) lawsuits over Domain name ownership can cost you more than that in lawyers fees ..
Small hosters who try to get greedy usually dont last long ..
1. which domain reseller is better for this kind of business, godaddy? enom? or reseller club and why?
specific hosters and domain name services dont get discussed in the non subscription part of these fora..