it all depends
but Here is a REAL basic structure
lets break this into 2 different questions.
1. pooling investor money is illegal unless you use a Regulation D 504, 505 or 506 and you need a SEC atty to put the PPM (private placement memorandum together for you)
once you have that (from 2500 to 25,000 bucks) you can start to raise money but only under the guidelines of the regulation you chose.
you may however, under MOST states rules, create a NOTE on the property and be exempted under sales of "partial or full mortgage" sale. you need to look it up for your state.
for what your doing, I use private money, or hard money from 1 investor. I get the rehab funds in escrow, with an agreed upon draw down schedule. step one buy the property, step 2. do 5K in rehab, show the rehab, show the receipts, get 5K out of escrow, do it again until done. step 3. sell house.
if you pay for the payments during, before or after, is only dependent on what the investor requires. when I can I put all the payments on the back end. because it doesn't affect my cash flow. I pay a bit more in interest, but thats ok.
I loan hard money, and when I do loan, I require that they make monthly payments of Interest only. reason is. I can tell when something goes wrong, I don't have to wait 6 months to find out.
most money is patient enough to wait 6 months to 12 months to get paid. they get paid out on closing. or on a refi. I typically wont carry the note for an investor if they are selling it to a retail person. I want my money back so I can reloan it.
the format of your question is kinda broad, so I hope i touched some basic points. its kinda like asking, how do you make money....
hope that helps