My wife has made homemade yogurt for years.   Her first maker was one she had back in her college days and she recently got a new one again.   We have our own Jerseys so she uses whole milk but she says it will work if the cream is skimmed first.  Her new yogurt maker has temperature control too so she can change it according to what the culture requires.

She buys the original culture and then saves some from a batch for the next time and uses different kinds at times