Yes, you must report the income. Many people believe the "vacation home" tax rules apply to exempt such income from tax, but those rules do not apply except in very unusual circumstances.
In determining your taxable income from the rental, you are allowed to deduct maintenance fees, property taxes (if separately paid, such as in California), interest expense on your loan, rental advertising, rental commissions and depreciation. Any other expenses directly related to the rental would also be deductible.
Depreciation would be based on original cost, if you rent it before ever using the week for personal purposes (including an exchange, use by family or friends, etc.). Otherwise, depreciation is based on the lower fair market value in your sales market - the resale marketplace - as of the date you first rent the timeshare. The rate of depreciation should be 3.485% of the allowable "cost" (as discussed in this paragraph). In later years, the depreciation would generally be 3.636% of that same number.
Travel expenses to visit the timeshare and other expenses that are generally related to taking a vacation and only incidentally related to renting the timeshare are not deductible.
If you have a net profit after claiming the allowable deductions, it's taxable. If you have a net loss, it's almost always not deductible, but the loss can be carried over to future years.
See post #4 in
this thread for more info on the rules associated with the taxability of timeshare rental income, including why losses aren’t deductible and why the vacation home tax rules don’t apply.