I've sublet before in Irvine but this was years ago.

Interview and select your tenants carefully. Even if it's take months. You're buying cash so you've got time. Picking the right tenants will save you a lot of headache. You shouldn't have problems given the demographic of Irvine. I opted for young professionals (ended up with girls). Ask them question to get a sense of how respectful they are, cleanliness, experience living with others, what are their pet-peeves, how they handle conflicts....etc. Have your relative present too so there are no surprises for anyone.

Always do background check, call their references and sign a contract.