Considering how fast things are changing on the various Caminos, and the fact that such a venture is a long term one, I would not base my decision on current scarcity of accomodations. Take for examples all the new accomodations between Santiago and Finisterre and Muxia that are now available. Would be a pity to invest in a property just to find out somone has done the exact same thing 1 km before you, especially if you are not in a area you love.
Also, as the roads do not always take you (thankfully) along the Camino, I would not drive around to find a place but walk the Camino. Walk it slowly, learning about the towns, villages, bus services, trains, where you could find the supplies you would need to run your albergue. That is, in my opinion, how you will best discover what pilgrims experience, when they may be struggling, when they may ready to stop, where they may love to stop to enjoy the area and not just walk through it, as well as gage manageability of the operation. You can also listen to pilgrims and do your market research that way.
I have seen many lovely people running albergues that were special in their own way, yet struggling to get them filled, while people raced to get a bed elsewhere. I think this has to be a labour of love, a lifestyle you choose for yourself, and not an income you would depend on, at least initially.
I wish you the best of luck and would love to hear about your process as you develop this project further.