How soon after viewing to make an offer?

The first bidder always has a slight edge. Some sellers want a quick sale to a reliable buyer.

For them, time is of the essence. If you delay, you will miss out. 

For others, top money will be more important.

By putting in the first realistic offer you are laying down a marker, showing your sincerity and building goodwill.

If you want to put in a cheeky low bid and don’t mind losing out on the property, wait a couple of months.