· Retired citizen
You can use the cables and brake lines that are on the bike now as long as you don't get taller bars. Of course the cables are going to be to long if you go with the stock Sportster bars but they'll work for the time being.I believe they are 12", and I know that the previous owner did change all the cables to longer braided cables.
This being your first bike and first Sportster I advise you that installing new cables won't be a cake walk for ya, especially the clutch cable and front brake lines.
I suggest to ride the bike as is for a season, get the service manual to read while sitting on the shitter and change the bars over the off season after you've schooled yourself !