I’m lost here, why are u “always” looking for free options?
Doing research requires assets and budgets, as a PRO you must ask for that stuff to your line manager.
Providing the right amount of money and/or a gift will put the user in a better mood to be focused on the task and to provide a high-quality feedback.
At the end you are looking for valuable feedback to improve your product (that I guess is not for free), aren’t you?
Friends and family can be a good starting point but you cannot develop a product only with them