None of these questions I can answer for them, as there are too many variables.

How much demand is there for what you do or sell ?
How much competition do you have ?
How well linked and ranked can you make the site ?

And on and on and on, which makes predicting when will it pay for itself ... much less make a profit, impossible to say.

This sounds terrible I know, but if you were to try and set up shop in real life, you would get told the same thing, that if you don't have enough capital to float for a year without a major profit, you can't afford to go into business.

Now, to those who tell you otherwise, they are, " mis informed " . Link building  takes time, the research and trial and error of what keywords to use, takes time. Getting good ranking and high listing for your keywords on the engines, takes time. And the most important of all, getting the right traffic to your front page, takes time.

These are all analogous to what a real life shop does, advertisement, getting listed in the phone book, having signs out and flyers out etc. Until they are
" noticed " by the local community and have customers, seeking what they sell, walking in the door. And the Net community is a LOT larger.

Now is there anything you can do to speed this up ? Sure there is ...

Research:
Go to the engines and plug in your topic type and see what the others, that are on those first 5 pages have done. Back track their link set up. Figure out what key words are most commonly used for your site topic. Go to anyone of a 100 keyword suggestion tools and find more.

Plan your keywords:
Now use those keywords you found on that most important front page and everywhere else. Use them in the header, meta tags, and title slots. Never mind your company name, as no one knows it .. YET! But plan out the text so that the keywords a potential viewer might plug into the engine as search words is ON your pages, often.

Link, Link, Link:
Link the site up to as many different " related" sites, engines and directories as possible. And keep doing it !

Stay focused:
Pick a topic type and stay with it, you can diversify, but be sure that you stay within your topic type. I.E.: Yes you could sell luggage alongside of herbs, but I wouldn't recommend it. Why ? Lack of focus. The engines categorize your site as belonging to one basic genre. If you try and spread it out too far, in the hopes of covering all possibilities, you dilute its potential. Pick a topic and stay with it.

Hire a good designer:
Yes, you can do it yourself with any number of online builders, however its going to tend to look like it. You need to be one of a kind to stand out. And unless you have the time to devote to learning all the details of what makes a site work, hiring it done is much more cost effective and should net you better results.

Pick a good host:
Since you now know you will have to wait before the site pays off, pick a hosting that you can afford. If your host is costing you more than 10.00 bucks a month your paying too much. Even at that, that's 120.00 a year, you do the math. So be sure to choose one that you can afford to absorb the cost of maintaining it, while you promote it.

Get on the engines:
This is the last  yet most important job, getting on the engines. The Net is much too large now for the old ways of surfing the net. The engines are the only way to find anything. If your not in them, you don't exist.

I wouldn't bother paying to be on any engine, as again it can take months before you are " noticed". It can take months to get into the top spots. So why pay for a listing in 72 hours ? Your throwing money away. Even if you could somehow grab the first spot right off the top, people will go with who they know, first, with what is familiar, before they will try an unknown.

Spread it out and get known:
If no matter where the viewer goes in your topic, there you are, just by sheer repetition they will eventually notice you and come take a look. So hook it into directories and other sites of related goods, as often as possible.

Make all your customers happy customers:
As with our cousins, the brick and mortar shops, the best advertisement costs you nothing at all, word of mouth. Or in the case of the Net, the written word in a e-mail, or group posting, singing your praises. This is where your " fame" spreads. Your best and foremost tool for any business is your reputation, make it a good one.

All Businesses are a risk:
Keep in mind, even if you do everything right you can still fail, simply because of factors outside your control. If you sell luxury items for example, which is most of us, and the economy takes a dive. It won't matter if you have the best priced luxury goods going, if the buying population is struggling to pay rent, your not going to do as well. There are ups and downs to everything, some months you will do well, others you won't ... period.

There is no such thing as get rich quick on the Net or in real life. The net allows us to take that risk in a much less costly, if done correctly, venue, to where we can afford to try it and see where it goes, but it takes work and time. In the meantime, hang on to your day job :)

More soon
Esta