Hi Stefan,
I ran into this last year on a SFH REO. The PUC requires that the gas line be cut at the main if the gas has been shut off for over two years. Since the line was so old, I needed to have a new one run to the house. Thankfully it was a short run (~15') and I had someone do it relatively inexpensively. Note that you need a DOT licensed plumber to do the work and it needs to be inspected by the gas company, so it will take several weeks. Good news is that it's finally warming up in Pittsburgh so you'd be fine without heat for a while (assuming that you've got some rehab to do).
But you'll just have to run the numbers and see what makes sense for you. It cost me $1100 to have the new line run, which was well worth it considering the house had a newer furnace already installed. Funny thing is that the gas company was offering rebates for new business accounts up to $1000 towards the cost of having a new service installed (which this technically was), so it only cost me $100! Installing a mini-split system can range anywhere from a couple thousand on up depending on the size of the house. Are the utilities already split? That may make a difference as well.
Ryan