You can’t just tell someone to leave without going thru a legal process.

as much as I legally can: 750

They are there to help and to protect your interests - to ensure things are legally done and to ensure the deal closes. 

If that doesn't work, consider taking legal action (posting a 3 day comply or vacate) and at the very lease make sure that you:1.

I also would pick a more detailed rental agreement over a general one that may not protect you in certain legal situations.

I'm just starting out as a Real Estate investor and looking into educating myself a bit on the legal and tax aspect of owning investment properties.

I doubt it allows for 2 units (it’s probably SFH.) assuming that, you can’t make it 2 legal units (adding an ADU is different, as I don’t think you’re allowed to take space from the main house for the ADU- it’s usually added sq footage.) and even if it allows for 2 legal units you may have to add a second parking spot, separate utility services (read: expensive and a PITA to install.)So the simple plan is to basically do the minimum work needed, as you describe, without permits just to separate the 2 living spaces out.

Good faith (or goodwill) is something that is paramount in business and I believe is also a legal term.

Do not rely on it for legal advice.

@Bryce Baker Get everything written on paper as if it's a legal binding partnership with your family.