First, be advised. I am not an expert in anything except my own experiences. And my experiences are confined to a particular time and place. If you have issues, I welcome them in Comments.
We've been house hunting in Herault on several occasions since 2003. (Herault is a French department, somewhere between an American county and a state.) We twice visited to find a holiday home from which to learn about and explore the region. After deciding that this region of France was where we wanted to settle in our retirement, another search led to our current home of seven and a half years. And recently, we searched for a home with broader, gentler stairs given the state of our old bones. So I do speak from experience. As always, my advice is free of charge and worth every penny.There's no multiple listing service in France. Each agent has their own website and, while some agencies do cooperate with partner agencies, it can easily be the case that there is a house for sale next door to the one that you are viewing that fits your requirements, but there's no sign out front (There are seldom street signs in our region.) and your agent doesn't have a clue. That's one reason to employ a more scattershot strategy than you might in the USofA.
The internet is your friend and there are multiple ways to take advantage of what the internet has to offer.
Once you have picked a region, do a simple Google search. And yes, even though you will be searching in France, such search terms as 'real estate Languedoc' or 'real estate Herault' work just fine. You can even take it down to an individual town . You'll get a bunch of hits - pages and pages. Take the time to poke through several of them and you will be rewarded. Fortunately for those without working French, most of the sites do translate into English. Eventually, if you expend time and effort, you will learn which sites seem to handle the type of properties most suited to your requirements. You may notice that some agencies update their websites frequently, some not so much. Decide for yourself what that might indicate.
And then there's Facebook. Lots of pages and groups cater to anything and everything for sale as well as sites that are specific to real estate, to French real estate, to French houses in a specific region, to French houses under 50,000, and so on. My brief and recent experience tells me that Facebook is becoming very popular for both sellers and buyers. Whether you like or hate Zuck, his Frankenstein monster is hard to ignore.
Never undersetimate word of mouth. Bakeries, butchers, supermarkets, and other high traffic venues often allow the posting of community announcements. Tabacs, the only stores allowed by law to sell cigarettes and other tobacco products in France, can be important community gathering places. The folks in the mairie, the city hall, usually have a pretty good handle on what's going on in their town. And in the village squares and in cafes, there are likely to be men and women who will be happy to engage with a stranger, even one with fumbling French, as long as the effort is sincere.
In sum, if you are looking to buy a house in France, there are multiple avenues available to assist you. Make a list of your requirements - important questions from buyers in our region include the nature of the outside space, is there a garage or available parking nearby, distance to local services, and such. Let your contact know how important those requirements are. Stick to your guns. And get to it.
A journey of a thousand miles begins with having enough RAM.