If you have a Master's degree, a Ph.D. should take you ~4 years generally.
If you only have a B.Sc. there are usually two routes. The master's to Ph.D. route, where you enter the master's program and transfer to the Ph.D. should take you ~ 4 years. If you decide to get a master's and then a Ph.D., it should take you ~6 years (2 for the master's and 4 for the Ph.D.).
As for the cost, these positions are usually funded, so you should actually be making a small amount of money.
Normally PhD will take between 3 - 4 years regardless the subject of study. For PhD, I suggest you to find scholarship, it should be not hard to get as for PhD studies mostly students work for a project owned by a group of researchers (professors) that have got research grant. Just search the internet, this site may help: http://world-edu.info/scholarships/2010 … -in-swiss/