Taking over parent's house

[Ying Lan]

Hello~ My parents are selling the house they've lived in for 20+ years.  We're thinking of taking it over and renting it.  Need advice on the best way to transfer the home from their name to our business/corporation name that's beneficial to both parties.  Believe they won't need to pay capital gain because it's their primary home.  If they were to "gift" it to us, does that mean we have to pay the capital gain (calculated from when they first bough the home 20 year ago?) if we decide to sell it down the road? Is it better to treat it as a standard buy/sell transaction so they won't have to pay tax on the capital gain and we can start the "gain" based on the sell price?  We also want to choose the option that's most cost effective (lawyer fees/trasfer fees/realtor fees, etc.) Any advice will help tremendously.  They're located in Cook County, Illinois.  Let me know if additional information is needed.  Thanks in advance!!