https://www.irs.gov/publications/p463#en_US_2017_publink100033749
For tax purposes, travel expenses are the ordinary and necessary expenses of traveling away from home for your business, profession, or job.
An ordinary expense is one that is common and accepted in your trade or business. A necessary expense is one that is helpful and appropriate for your business. An expense doesn’t have to be required to be considered necessary.
This is certainly a necessary expense, but the IRS may dispute that it is "ordinary".
You are traveling away from home if:
Your duties require you to be away from the general area of your tax home (defined later) substantially longer than an ordinary day's work, and
You need to sleep or rest to meet the demands of your work while away from home.
Presumably, you must be physically in LV, so the first is satisfied, and LV is far enough away from SF that you wouldn't be able to go between them without rest.
If you have more than one regular place of business, your tax home is your main place of business.
So that would be SF.
You can deduct ordinary and necessary expenses you have when you travel away from home on business. The type of expense you can deduct depends on the facts and your circumstances.
Table 1-1 summarizes travel expenses you may be able to deduct. You may have other deductible travel expenses that aren’t covered there, depending on the facts and your circumstances.
You should consult a tax professional, but it looks to me that you would be able to deduct any expenses reasonably necessary for the job. You probably will be limited to the income from the other job, however. That is, if you end up spending $12k on travel expenses, and only make $10k at the other job, you probably will be allowed to deduct only $10k.
