I used $80k to pay off personal debts and $50k to remodel it by myself with my two hands.

We don't believe in co-signing for anyone.My main question is, as my wife is a remainderman, will she be giving permission for her mother to get the loan or will she be co-signing the loan?

When the IRA invests in real estate using debt not only does it have to be non-recourse but the IRS says, you can use leverage but since you aren't only using IRA money for this investment the retirement account is going to pay UBIT on the income generated because of the debt. 

Our main issue is these properties are owned in an LLC.

Quote from @Franklin Marquette: When building ADUs, do they generally create value uplift for the property in the same way that the main house is valued?

I mainly bought it for the land, do not intend to rent it out for cash flow or what not.It is currently occupied by the previous owner.

I'm getting ready to list my first large property with 3 separate units (Main Unit, ADU, DADU) on a SFH.

Also, you will likely only be able to use the rent to offset the mortgage pmt debt on the rental property to $0 since you dont have any Sched E history yet. 

With 0% down and 30 year amortization, your monthly debt service will be $1756.

It's an acreage property near the lake that has a main house (2/1), guest house (3/2), and small studio-layout unit (3 units on same property).