Let's simplify buy-to-let. It's just buying a property with a specific mortgage so you can rent it out. The move isn't just buying it; it's running the numbers before you buy.
A simple check: Will the rent cover the mortgage and all the other costs (insurance, management, maintenance)? If yes, you've found a potential cash-flow property.
What's the biggest question you have about how buy-to-let actually works?