Buying a SFH with a rented ADU that is un-permitted (First time buyer)

[Elijah Householder]

Hi all, 

I hope everyone is having a good weekend! 

I am newer to this forum so apologies if I am posting in the wrong place but I have a couple questions about purchasing a SFH with an un-permitted ADU. This is my first (possible) home purchase so I am super excited about it but trying to be smart.

So I have been fortunate to come across a SFH where the owners do not want to post the house they just want to sell it. They are actually neighbors to my parents rental so we have some relation to them. Those who are in socal and I am sure most markets know how tough it is with the bidding wars so I think this could be a good deal.

So as mentioned it is a SFH however there is an unpermitted three bedroom ADU in the back. It is built very nicely and currently being rented for a pretty good price. But here are my questions -

1. Is there any risks I should be aware of when purchasing a house with an unpermitted ADU? I have been reading online about this and I am hearing very mixed feedback. 

2. If I purchased it and actually end up occupying the ADU and renting out the main house would that help with avoiding any risk from the ADU? I know a lot of people say there are insurance issues and the tenant can sue for things if it's not permitted but if I was the one occupying it and renting out the main house would that be better?

3. I believe I know the answer to this one but can you consider rent from an unpermitted ADU to qualify for the loan? They have consistent rent payments but from what I've been reading it sounds like there is no way to use this to qualify.

Thank you so much in advanced!