sourdough starter got mouldy

I tried three rimes to get a sourdough starter and each time it got mouldy. I tried it with rye, is wheat easier? What could go wrong? Was the house too cold?

Mold takes days/weeks to grow and fruit. Yeast takes minutes/hours. I wonder if it would be appropriate to refresh the starter more frequently? At a bakery I frequent, they use a portion of the existing sourdough starter to make a new starter every day. It doesn't sit around long enough for mold to grow. Even if they aren't making sourdough bread that day, they still make a new starter.

Yes, I agree with Joseph.

Whenever my sourdough goes mouldy I throw it out, wash the container well and sometimes sterilise the container and lid with heat, and start over. I start with just whole wheat flour and water, and usually after a couple of days I'll make my first batch and it doesn't rise very well, but then I use a little of it to start the second batch, which usually comes out well. It goes mouldy if I don't use it / refresh it with a week. It lasts longer in cool weather or the fridge, and can go mouldy in just a couple of days in hot weather.