Is it wise/ethical to take up a TT position with a desire to leave? I'm currently deciding whether to take up a tenure-track faculty position. It's a good position (R1, top-50 department in USNWR ranking), but I'm not very excited about it. In particular, the location is not to my liking. So I would seek to move elsewhere if I took up the position. That is, I would conduct another job search in 2-5 years.

This seems to me to be potentially unwise (as I have been told that it is hard to move between TT positions) and it also seems potentially unethical.

My alternative is to do another postdoc and try the job market again in 2 years or so. That also seems potentially unwise, as I have no idea what the job market will be like then and I may end up with even worse options. I'm also worried that I'll start to look "old" as a candidate, as I'm already 2 years out of my PhD.

I have talked to a few people. They have given me conflicting advice and they are not particularly able to relate to my situation, so I want to ask for some other perspectives.

My specific questions:

1) Is it unethical to take up a TT position with a desire to leave it? I.e. would it upset people when I end up searching for another job.

2) When evaluating TT candidates, does it look better to have 2 more years of postdoc or a few years as an Assistant Professor?

3) In general, is a second job search usually more/less successful than the first one? What factors might determine this?
No, it is not unethical. When you accept a job, in academia or anywhere else, you imply a commitment to do the job in the immediate, short-term future, and nothing more. What that means exactly is somewhat context-dependent, and in academia that minimum period is usually interpreted as one year. 

Leaving a tenure-track job after only one year may leave people at your department a bit disappointed and potentially sour your future relations with them a bit, but I have never heard anyone argue that doing so (or even having the intention of doing so) is unethical, and don’t believe a reasonable person would adopt such a position. All the more so with a plan of leaving after 2 years or more; I simply cannot see how this can offend anyone’s moral sensibilities.

As for whether such a plan would be wise: it may or may not be, but your explanation of what’s driving your doubts about this makes me think you are overthinking the matter. It is no harder in general to move from one tenure-track position to another tenure-track position than it is to move from a non-tenure-track position to a tenure-track position. Depending on the precise circumstances, it may be harder, or less hard, or (most typically IMO) would be exactly as hard. Everything depends on how attractive of a job candidate you will be 2-5 years in the future, which is a function of how attractive you are now and what you’ll be doing between now and then. One particular factor that could actual play in your favor is that already having a tenure track position in an R1, top-50 department could give you a stamp of legitimacy that would make other departments of equal or lesser (or even slightly higher) stature more inclined to view you as a strong prospect for hiring.

Finally, another thing to consider is that, while you think you don’t like the location of the place where you have the current offer, your opinion about this might change in the future. People generally tend to overestimate the extent to which they can predict what their future selves will want. Which is another reason the whole ethics question here doesn’t really apply in my opinion - you should reserve your ethics-based doubts to actual actions (which in this case are also okay ethically given what you are considering doing), and not to tenuous intentions that may or may not ever translate into actions.

Good luck!