How long it takes you to produce 100K words depends greatly on how quickly you write, how much time you have for writing, and what level of polish you want your words to be at.

For first drafts, most writers can produce 100K words in 3-6 months, depending on the amount of time per day allotted. The truly fanatical (like those 2xNaNoWriMo maniacs mentioned in @One Monkey's answer) can finish that amount of writing in one month, while an upper limit might be about a year.

Every writer I've ever talked to recommends taking at least a month off after finishing the first draft in order to get some critical distance.

After that comes editing, which is a highly idiosyncratic process. Some people make multiple passes over the draft, making small tweaks each time. Some people rewrite whole chapters at once. Some people only write one second draft, which changes everything at once. How you decide to edit is up to you, but again I'd suggest that 3-6 months is a reasonable time frame for editing. Note that some people spend a long time in this phase--Patrick Rothfuss famously spent 14 years editing his Kingkiller trilogy before finding a publisher for it.

Overall, the novel process takes about a year if you work consistently, maybe more or less depending on how much time you can devote to it.