<human>: Hi,

Potentially have a situation work-wise that I have never faced before so thought I would ask around to see what the etiquette should be. 

**Situation**

Work in IT for a finance company on the east coast of the US. Got contacted by a competitor on the West Coast for a similar position. Been through interview with HR and manager/team member and the company seem interested in hiring me. Since the company started interviewing me, my gf has been diagnosed with breast cancer and has gone through surgery (all super quick, maybe all that health insurance cost is worth it in some cases!). Initially, it seemed like there would be no chemotherapy prescribed but that has changed. Basically means that until the end of October, she will be receiving treatment (chemo until August, and radiation until October)
* Now, here comes the predicament. We both would love to move to the West Coast and I am very interested in the job, but there is no way I would want to move while she is receiving heavy duty treatment. This is the timeline that I can see them wanting if I were offered the job, seeing that they are aware of how long a visa transfer takes
Mid July - receive offer
End of July - Accept negotiated offer, submit visa transfer material
Start of September - Hand in notice once visa has been transferred
Mid-late September - be ready to start + have moved

What I am thinking of proposing is to stay with that timeline and work from the East Coast, with maybe a couple of week-long trips, until end of October due to personal circumstances (would I be expected to reveal what they are?). They have an office in my city that team members from the West Coast travel to regularly, so this could be possible.
OR asking for a start date of the end of October.

Is there etiquette that I should follow in this situation? 
Also, should I tell them about this now (still dont know for sure if I will be offered a position) or wait until the offer / negotiation stage?

Can you provide a brief overview of the text?
<bot>: Personal situation means that I wouldnt be able to start a new job (in person) until 2ish months after they would potentially want me to start. How should I approach?