You need to clarify with Bob what your agreement is. If you and Bob are working together on these jobs as partners, you should get a written partnership agreement done by a lawyer who works with software industry entity formation. You can legally be considered a partnership if you are operating a business together, even if there is nothing in writing. The partnership will have its own tax return, and you each will be allocated 50% of the profits/losses (if that's what you agree to). This amount will be reported on your own individual 1040 as self-employment income. Since you have now lost all the expense deductions you would have taken on your Schedule C, and any home office deduction, it's a good idea to put language in the partnership agreement stating that the partnership will reimburse partners for their out-of-pocket expenses.
If Bob is just hiring you as a contractor, you give him your SSN, and he issues you a 1099, like any other client. This should be a situation where you invoice him for the amount you are charging.
Same thing with Joe - figure out if you're hiring him as an independent contractor, or if you have a partnership.
Either way, you will owe income and self-employment tax on your profits. In the case of a partnership, the amount will be on the K-1 from the partnership return. For an independent contractor who's operating as a sole proprietor, you report the income you invoiced for and received, and deduct your expenses, including independent contractors that you hired, on your Schedule C.
Talk to your tax guy about quarterly estimated payments. If you don't have a tax guy, go get one. Find somebody people in your city working in your industry recommend. A good tax person will save you more money than they cost.
IRS Circular 230 Notice: Please note that any tax advice contained in this communication is not intended to be used, and cannot be used, by anyone to avoid penalties that may be imposed under federal tax law.