When (or if) to introduce a second cat?

[welshbubba]

So we lost our beloved cat 2 years ago. Not long afterwards we started looking at moving house and decided to delay getting another cat until we were settled. We're now in a house with a lovely large garden and ready to have a cat again - in fact we hoped to have two this time. In the meantime my parents have been "adopted" by a stray who started appearing in their garden looking rather thin. Turns out this cat had been stray for 18 months before they took him in, after wandering away from home. He is chipped but his owners are not in a position to have him back. So my parents have been looking after him on a temporary basis with the plan that we would take him once our house move was sorted. My question is about potential cat number 2. If my parents cat comes to us would it be better to introduce another cat (we'd be looking at another recue cat) at the same time, delay it for a while, or is it best to stick to one cat only. The cat we are having is about 4 years old, and seems quite placid. Thanks for your advice.