Honestly, I had goldfish live for three years in un-conditioned tap water for three years before we moved out to a place where we have a well. It will be fine until you get some water conditioner. Up until you get conditioner change 1/2 of the tank's water twice a week. After you get the water conditioner, if the tank is less than 20 gallons, continue to change 1/2 of the water twice a week. If the tank is 20 gallons or larger change 1/2 of the water once a week for five weeks. After five weeks you can fall back to 1/2 per week (In < 20 gallons) or 1/4 per week (in >20 gallons).
If your tank is less than 20 gallons, upgrade within the next year. If your tank is 20-30 gallons upgrade within the next year and a half. If your tank is 30-40 gallons upgrade within 2 years. A more accurate way of telling when you should upgrade is watching to make sure your fish can swim 4x it's length in one direction at least and turn around with room to spare. When the fish cannot do this you should upgrade. Regardless of how long/wide the tank is, a goldfish should have at least 20 gallons to itself due to biological reasons (basically, otherwise there is not enough water to support the fish.)
~Yes you can put the fish in tap water for now. Get conditioner as soon as you can. Chlorine and the other chemicals can do irreparable damage to your fish.
~Do 2x 50% water changes twice a week until you get conditioner.
~Keep waste levels down though water changes (ammonia =0, nitrite = 0, nitrate = <20) until tank is cycled by doing 50% water changes at least once a week.
~After the tank is cycled, do weekly water changes of 25 to 50%.
~Upgrade the tank as needed to make sure the tank is enough for the fish. A common goldfish will eventually require at least a 4foot by 14 inch tank. A 75 gallon works well.