24 hours generally is considered reasonable notice. The realtor should come over only during normal business hours (unless you agree otherwise).
Disclaimer: This post does not constitute legal advice and does not establish an attorney-client relationship.
The law considers 24 hours' advance written notice to be reasonable in most situations.
Special rules apply if the purpose of the entry is to show the rental to a purchaser. In that case, the landlord or the landlord's agent may give the tenant notice orally, either in person or by telephone. Again, the law considers 24 hours' notice to be reasonable in most situations. However, before oral notice can be given, the landlord or agent must first have notified the tenant in writing that the rental is for sale and that the landlord or agent may contact the tenant orally to arrange to show it. This written notice must be given to the tenant within 120 days of the oral notice. The oral notice must state the date, approximate time and purpose of entry. (California Civil Code section 1954(d)(2).)
The landlord or agent may enter only during normal business hours, unless the tenant consents to entry at a different time. (California Civil Code section 1954(b).)