I’m assuming you are referring to the Rover 5 with the mechanical brakes. The new Rover 6 plus has hydraulic brakes, so the brake lines are sealed.
It’s very easy and cheap to replace mechanical brake cables. If the cable is just frayed on the end and not real dirty inside the sheath, you can install the new cable in about 10min. Loosen the cable at the caliper. If it’s frayed, cut the fray away. Then go to the brake lever and pull the cable through the sheathing. Glide the new cable through the sheathing, starting at the brake lever. Once through, fish the cable through the caliper bolt, adjust brakes and tighten bolt.
If the sheathing is dirty, you need to buy a cable with sheathing. Cut all the zip ties holding the cable and route the new cable the same way and zip tie it back together. Maybe 30 minutes at the most.
I wouldn’t be afraid of mechanical brakes.