I have purchased the car siding to put on my floors. I know I will not be happy with the edge along each board. Those will leave an area on my floor to collect dirt and grime. I want to redo all those edges. I have 125 boards that are 12 feet long each. Would it be better to buy my own router table and router and redo all
the boards myself, or would it be more cost effective and easier to find someone in my are with the proper router table and pay them to do it?

Not sure what you mean by car siding. Have you considered using a Polyurethane coating over the top? A couple of nice coats of Poly will seal everything up to a water tight and non-dirt catching finish. That’s how hardwood floors used to be finished. Don’t know if they still use Poly or something else these days. My dad used Poly on his hardwood floors in 1962 and they haven’t got a scratch in them yet. And they raised 4 kids in this house.

I am planning to use polyurethane… what I need to know is… more in reference to the small grove that is going to be left between the boards when I put them down. Not sure if I should invest in a router and router table. Each edge will have to be cut off, and then a tongue and groove put in. I will also need advice on what brand of table and router will be the most economical, or if the advice is to hire it done.

I think the first thing I would do is to find a company that specializes in Hardwood floors then take a piece of the wood to them, tell them what you need done to the wood and ask them how much to do all of it for you, because a planer/joiner and a couple of routers are kind of expensive, and since you will be working with 12 ft long boards, you will probably need to build your own router table so you can keep the boards flat and

Are they smooth on the back too. If they are install them upside down. If not, install them upside down anyway, then rent a floor sander for a day from your local rental place for less than buying a router and bits. Then Finish it. Definitely a do it yourself project.

I admit I don’t know “car siding” is. Does it already have tongue and groove? Or is it just straight edge? If it is just straight edge and you want to butt the edges together, you will need to true the edges, BUT you must keep the board width constant(a planer/joiner). If you want to make the boards tongue and groove, you can buy the router bits to accomplish this, but I would suggest 2 routers one set to cut the grove and one set to cut the tongue, mounted in a large table