Once a syphilis chancre starts, how long does it take to develop?

Starts?: Your questions this morning are very curious. What do you mean by 'start's. An infection either happens or it does not. Syphilis can take six weeks or more to show up after an exposure. But, if a sore happens then one needs to get the sore evaluated urgently. It is better here on the internet to ask specific questions or description of the exact thing you are feeling or seeing.