Your profit is going to be determined by your markup price. If you mark up the price of domains by $1/year, then your profit is only $1. If you mark them up by $20/year, then your profit is $20.
All registrars offer free whois, unless you're thinking the privacy option, then that's different.
I would avoid contracts, especially if you're a new host. Most users tend to avoid them. Contracts would be different if you were offering dedicated/colocation hosting, or possibly even reseller hosting. But with shared hosting I would steer clear from the contracts.
With your plans, I wouldn't worry too much about pircay/warez groups. They're not going to purchase a plan with 300MB, on the average a single ripped movie is roughly 600-700MB. Some are DVD rips, so they are 4GB or more on average.
On the flip side even if the software package they pirate is 100MB, they would only be able to transfer it 3 times before running out of their monthly quota.
No group would sign up for a plan with only 300MB, they're probably looking more towards the larger packages, offering dedicated bandwidth, and probably offshore hosting. (Side note: Does anyone remember that oil rig that was out in the Pacific I believe that the US deserted? Some guy claimed it, and registered it as an independant country and now provides colocation/hosting from the rig. The name escapes me but I thought that was an awesome idea. Could you imagine having your own country!?)
Back to the point, if you decide not to offer a 30 day money back guarantee, I would at least consider a 14 day money back offer.
I would estimate that the majority of users out there have no clue there is a panel to even manage their hosting with. Out of those that do, however, I would guess that more than HALF of them prefer cPanel. But the choice is going to have to be yours. You HAVE to find that niche market and target it.
Against, most customers are not going to care, or possibly even know if their hosting is Windows/*nix based. Those that do, or that it would matter to would probably lean to *nix hosting - especially as the majority of web apps out there use *nix.
If you offer Windows hosting it is going to have to be your call whether you charge more. Most providers do because of the amount of updates to apply, and the amount of abusers targeting Windows' exploits. Thus the maintenane/support of these machines are more demanding, which makes them more expensive, which drives the cost up. Thank the abusers.
The problem with the disk space/transfer configurations is that for someone to use just 400MB of transfer per month requires that they either have some sort of small application that is downloaded a lot. For instance:
The new IntelloDesk by ANM is roughly 3MB (I think) once it's rared. So for that alone to use 400MB of transfer per month would require that the file be transferred about 130 times. That is quite often within a month, about 4 times per day in a month. While that's easily obtainable with such a popular package as ID, and a company that can back advertising, a small personal site isn't going to have as much transfer - on the average.
Take a blog, blogs are mostly text. The user could have 4 visitors every day for a month. They could pull 3 pages of text from the blog every day and probably never hit that 400MB transfer limit.
You will, again, have to find your niche market, and target it. If it's a blogging community your package prices will be MUCH different than a file storage community, and VERY different from a community centered around art (music, graphics, etc...).
I think I hit most questions, and I must say VJ, at least you are asking around and researching before diving into the hosting industry. That is admirable, especially considering the majority of "companies" buy a reseller, throw a template up, add a couple PayPal links, spam a few forums, and call it a night.