Those questions will be left to those making the decision to by and willing to part with a large wad of their ready earned cash or perhaps a large wad of borrowed money for which more wads will have to be returned to the lender than was borrowed. Needless to say, this author thinks very dimly of all forms of borrowing, particularly when it will never have any return on investment.
What do you mean, never will have any return on investment? Well, how much do you want to spend? Do you realise that you're going to have to earn back that much in order to break into profit? How much profit do you think a single photo job will earn and don't give me that baloney about buying a camera and doing thousand dollar weddings every week. It's never going to happen. A newcomer is never going to get more than the crumbs that the professionals wouldn't touch and many professionals are going bust and going out of business. Perhaps you're going to compete with the $100 wedding photographers from Craigslist? How many of those are you going to have to complete to pay for the equipment - even if you get more than a single wedding?
Let's look at the costs of the cheapest shoot and burn wedding session. You have to meet the client the first time to peddle your wares. Then you have to meet them again to shoot the wedding. Then you have to hand over the CD within half an hour or meet them again at another date. With gas prices of $3.20 a gallon that's 3 trips. Even if they live within a gallon's travel then that's 6 gallons (1 each way) or $20 of income gone instantly. Add another dollar for the CD and case. Maybe you stop for a snack on the way. It easily becomes $30 gone so the $100 wedding is only getting you $70. Add any extras and that $100 could easily become far less.
Now let's have a look at cameras. For the serious and determined photographer there are two ranges - the mirrorless camera and the camera with a mirror. Both are available with a wide range of sensor sizes. This is where things begin to get a bit problematic. It has been argued that the larger the sensor, the better the image quality. A better starting point is just how big do you want to print?
What size are the common prints? The standard always used to be 6x4, 5x7, 10x8. People want everything supersized now so perhaps 11x14 or 16x24. There really isn't enough room in the average house or apartment to hang the latter two sizes.
So, assuming most people's walls are bigger and they want to use an 11x16 or 16x20 print then how many megapixels are needed? By my calculation and using 150dpi as a good measure, a 16x20 would be 2400 x 3000 pixels. Oddly enough that's 7.2 megapixels so an 8 megapixel camera should do nicely.
People get so bent out of shape by pixel density. Below 75dpi it's not really possible to see individual dots. 150 is really handy. 300 is overkill. Unless you put your nose against the print and use a magnifying glass, in which case you really need to get a life, then 150 is perfectly fine.
Where does all that leave the vast majority of cameras? Right in the available range - that's where. Nothing has too few megapixels to use. From the Nikon 1 to the Pentax Q up to the so-called full-frame cameras. Honestly, people make way too much fuss about sensor sizes. The sole time - the only time - when sensor size becomes an issue is with noise control. That only comes into play when you want to use high ISOs. Having used digital cameras for years, I have to say - I barely ever use anything other than ISO 100. I would have no qualms in getting a camera that had poor high ISO noise control on the basis that it would be acceptable on the basis that it's hardly ever an issue.
That leaves you, dear reader, with total access to the least expensive cameras. Given that the chance of reselling any of this electronic and camera gear for anything approaching a realistic price is absolutely minimal, there's absolutely no point whatsoever in spending a ton of money buying it in the first place. In fact, the less you buy, the happier you will be when it's time to dump it and move on.
My personal preference at the moment is the Nikon J3. The J1 was good but the J3 has vastly improved noise control. With the two available lenses, the range is from 27mm right the way to 270mm in a very small package. The whole lot would fit into a very small space. Not just that but with the way prices are plummeting, it's very affordable. In the days of film, I carried two bodies, 6 lenses and the whole lot weighed so much that if I moved quickly I could hurt my back. I believe I carried around 40lbs of camera gear. This has been reduced in the J3 to very manageable proportions. The J3 weighs 7.1 oz. The two lenses - the 10 - 30 and the 30 - 110 weigh 4.1oz and 6.2 oz respectively. That means that the whole lot all told weighs 17.4 oz or 1.01lbs or 494 grams. This is a totally insignificant weight for such power and versatility! In terms of cost, that whole lot costs around $656 which is near enough the entry price for just the camera with a digital SLR setup.