It’s never as simple as it first appears, which is why we always advise our clients to let the math guide the choice.

@Jill KellerI personally owned and managed several rental properties, mainly one family, 3-families and been advised by a number of attorneys through the years to forget doing LLC's.

They will advise you on how to proceed with your proposed ADU given your site-specific situation.For a condensed roadmap to building an ADU provided by wake county, use this link: Click Here

Any tips or advise would be great!

Readers are advised to seek professional advice.

For the office, it is advisable to begin with home office deduction if one meets the requirements of the law.

And for an OOS, I always advise to keep things simple at start, don't get greedy, go for quality and consistency, then work on maximizing monetization later. 

As others advised, get a structural engineer in there to review the conditions.

-> Besides doing your market research, i strongly advise that before any purchase or offer, that you hire professionals to help you in the process.

I bought my home in 1993, and some years back the prior owner neighbor advised the border fence is a few inches onto her property.