We have a potential home we would like to buy, however, it has baseboard heating and would like to know what is involved with this before we buy home

To create an estimate an on-site inspection would be required. Your best answer would come from getting 3 bidders to quote on the same work. This will be expensive if your baseboard is electric or hot water, forced hot air is neither so a complete furnace, and possibly AC, will be pricey plus the duct work. Duct work retro fit is seldom adequate or pleasing to the eye

I agree with ball. Many factors to take into consideration. How many levels, to the home, finished basement, etc, etc. Only way to get a good ideas is to do as ball suggest. Get some pros out to take a first hand look and go from there.