Welcome to Just Answer. I am here to help you resolve your tax and finance concerns. Please feel free to ask anytime you need extra help.
There are several different choices so I will review each of them for you with the pros and cons of each. Then the decision is your to make. Of course if you need clarification I will be happy to assist.
This is the simplest of the organization forms and can be conducted in your own name or by use of a trade name (DBA) which requires a registration of the DBA at the local county offices. If you select this choice your record keeping will be simpler than the other entity choices. You will file your business taxes using Federal Schedule C. There you will record the revenues (sales) and deduct the business expenses. The net income will be transferred to your personal form 1040 and to federal Schedule SE. Schedule SE is used to calculate the self employment tax. The self employment tax is Social Security and Medicare taxes combined. The pro for this entity choice is the ease of record keeping and tax reporting. The con is that you remain completely liable in the event that one or more of the ventures you invest in is sued. However, if these ventures themselves are operating as either a corporation or LLC your risk will be limited to your amount invested in that venture (unless you are convicted of criminal behavior - in that case no entity choice can protect you).
A corporation is viewed as a person created by law and as such must file returns for all its business activities. To properly prepare these returns will require a more complete accounting effort than a sole proprietorship but is not complicate. The returns are filed using either Federal form 1120 (C Corporation) or 1120S (S Corporation). The difference between the two corporate types is that the C Corp pays its own tax on its net profit and then any amount not passed to you as salary is taxed again as a dividend while the S Corp profit is passed to you (via a Schedule K-1) and you pay the tax on that profit whether or not you removed it from the business. If you do not remove it all in one year you may remove it in another without paying double taxes. As a separate legal person your personal assets are not at risk if the corporation is sued (see my criminal behavior comment earlier). The pros are the legal protections, the ability to shelter more money in a corporate retirement plan than a sole proprietorship. The cons are the additional record keeping, double taxation of a C Corp, and the additional tax return preparations.
An LLC is something of a cross between a Corp and a sole proprietorship in your case. It uses Federal Schedules C and SE like the sole proprietorship, has the simpler record keeping requirements of the sole proprietorship, and provides the retirement planning and legal protections of the Corp.
My personal choice would be a choice between the S Corp and the LLC. The essential difference to help make the choice is the cost to organize one entity type vs the other. LLC's require publication before they can be established while a corporate formation takes only a day or two. In NY the S Corp is far less costly than the LLC but in PA next door to me this is reversed. You will need to check the cost for each in your area. The reason you should check this is that the publication costs for an LLC depend on newspaper advertising rates in your locale.