I'm converting my garage into a Junior ADU and almost done.

If so the foreclosure sale has already occurred and junior liens have been wiped. 

You need to make sure the 1st lien lender allows junior liens for your downpayment before going down this road.

When I was a junior in college, my dad brought this idea up to me (he would help me purchase a SRH and I would rent out all the rooms and live in the master).

Superior lien holders typically are not parties to a junior lien foreclosure action.

@Jeremy HortonAs mentioned you don’t get title insurance but definitely want to check title as is it a hoa lien or 2nd lien foreclosing and you would still have to pay the first offWe invest in notes and just had a junior lien foreclose and someone bought it, renovated the home and we filed foreclosure and now they are going apoplectic thinking it’s their house and they fixed it and don’t owe us $.

Today I got a call from the football coach at the local junior college. 

Your private lender will be in a junior position on this deal since you have a conventional lender in place.

Hey @Summer Crawford I'm a junior in college (comp sci as well!)

then if you dont file the lien by the book material man can still sue for unjust enrichment and get a junior lien.