End user support isn't something that I really recommend a reseller use. One of the key selling points of a small hosting business, is that personalized service. If you go with a quality reseller, such as HostGator, while they may not offer end user support, what you are going to get is a quality hosting experience, which is another key of a good hosting company. I think it's more important to find a quality reseller, and then do support yourself. While it may cause you do a little more work in the short run, you'll likely end up with a much more successful business in the long run.
but is it not difficult for someone who is working at his job and just doing this reseller business for fun/partime to be able to offer 'customer support" 24x7???
A single human being cannot provide true 24/7 support. "Traditionally" there are some solutions to be able to provide it: outsource support, join forces with 2-3 other resellers and work in shifts, supporting each others' customers, get end user support from the reseller hosting account provider.
Out of these, I would go for the latter because the host will actually have true access to the server and is likely to be an overall better setup.
Whether the reseller ofers 24/7 support or not, one good reason to get end user support would be that, in the end, it is better for the end user's problem to be handled as soon as possible rather than for the ticket/email to wait for the reseller to wake up from his daily sleep.
Then again, markets that resellers should be going for are not necessarily expecting 24/7 support. As such, it doesn't have to be offered, nor provided.