1. Select forms showing "Form 1099" without additional "dash numbers" for general information.
2. Select forms showing "Form 1099-MISC" for any years in which you might be affected.
3. Select forms showing "Form 1096" for any years in which you might be affected.
You should get "general instructions," instructions specific to the "1099-MISC," and "sample forms." Both forms and instructions change yearly, so you should check back frequently.
In general, you have to send a Form 1099-MISC to each person who receives reportable income from you.
You must also send, to the IRS attached to a Form 1096, a copy of each 1099-MISC that you send to anyone.
A particular and unique "pain in the ass" is that you CANNOT USE DOWNLOADED FORMS for the Form 1096. You must get an "original" from IRS in order to send your report of 1099-MISC income that you pay to people. If their scanner fails to read the form you send in, they fine you $50, and they use "magnetic ink"1 so downloaded forms or other copies that you print won't scan.
1 It's not really "magnetic," but the specification for how to print a usable form runs about 300 pages, according to my recollection from when I checked a couple of years ago. You can't do it at home.
You do NOT generally have to use the official forms for the 1099-MISC reports that you send to the people you have paid, or for the copies you send to the IRS, but the "form" that you use must indicate that it is a 1099-MISC report and the proper line numbers and descriptions (as they appear on an official form) must be clearly shown. A couple of lines may be required even if there are no applicable payments, so read the instructions carefully.
You MUST SHOW A TAXPAYER IDENTIFICATION NUMBER on the form for each person to whom you make reportable payments. For most people, this is their Social Security Number. There is a very high probability that IRS will contact you and demand any omitted identification numbers.
The "investigation" at the border quite probably comes from the requirement that anyone not a citizen of the US must have an appropriate "work visa" in order to legally be paid for just about anything. It probably is illegal for them to receive payment, and for you to make payment, without appropriate prior arrangements. As I haven't run into a need to know, I don't have information on what limitations on earnings apply, or on what arrangements must be made. Given that there has been significant contention between Homeland Security and IRS about the lack of access to IRS information by Homeland Security, it is doubtful that information would be sent to IRS, but the immigration people can be a lot nastier than even IRS if they're offended.
I also don't know whether a visa number (assuming they're numbered?) would meet the requirements for a Taxpayer Identification Number; but the requirement to report any payments gives IRS a means to independently discover "illegal workers" and/or illegal payments, and if you own or rent a home, they know where you are.