You can start with gas and a phone. County records are the base layer and most of them are free to search: the recorder or clerk for deeds and liens, the tax collector for delinquency, the probate court docket, and the code enforcement office for violation notices. Some counties charge a few dollars per copy or put the good search behind a small subscription, and a handful still make you walk in.
The paid tools are conveniences that save time. A list-building service that combines those public sources runs somewhere in the range of $50 to $150 a month at the entry tiers. Skip tracing, which means looking up a current phone number or address for an owner, is usually sold per record, often a few cents to around 25 cents a hit, sometimes bundled. Neither is required to hand an investor something useful.
A course is not required either. What an investor wants is an address, the owner's name as recorded, what you observed at the property, and how you'd reach the owner. You can produce that with a drive and an hour in the county's website.
The part people skip is the paperwork before the work. Agree in writing with the investor what a lead is, what they pay, when they pay, and how long an address stays credited to you. Do that before you send the first one, because the disagreement always happens after a house closes, and by then you're arguing from memory.