Found a gas leak immediately after closing. Future advice?

[Bruce Clark]

Found a great property that was in great condition. The only issue was that the furnace was old but functional. I had an inspector look at the house and he did not find any major issues.

I closed on the property and listed it immediately. I had a ton of interest and found a great tenant (I hope) within a week. The day the tenant moved in, he attempted to get the gas turned on. Gas company found a gas leak and also said there was excessive carbon in the furnace. The red tagged it, and will not turn the gas on until i get it repaired.

Now I am stuck with these repairs on my first day of renting the property. My question is, did I make a mistake or miss something? Is there something I can do in the future to avoid this type of issue?