She may be getting alimony payments sufficient to allow her to qualify on her own.

Not sufficient for individuals' identification always, though.

Instead he/she claims that his/her invoice is sufficient.

You have the problem common to a lot of people getting started; wanting to invest but lacking sufficient capital.  

If you want to leave your IRA intact and avoid penalties or taxes, consider other options such as:HELOC (Home Equity Line of Credit): If you own property with sufficient equity, a HELOC can provide funds for a down payment without tapping into your IRA.Personal Loan: Depending on your credit, a personal loan may be an alternative.Seller Financing or Private Lending: Look into creative financing options for real estate investors, such as seller financing or private lenders, which can help with down payments without needing to use your IRA.

I am still not sure which one is sufficient for me to do.

The benefit of going conventional is being able to purchase an MFH without the stringent property guidelines, self sufficiency test, and longer escrow on an FHA loan. 

It also provides insights into your cash flow to help you make sure you have sufficient funds to cover your expenses.How to get it: The PocketGuard app is available for both iOS devices in the App Store and Android devices in Google Play.Cost: A free plan is offered with basic budgeting features.

also is $1.0M sufficient for Landlord liability?

Your primary insurance policy with $300,000 in liability coverage should be sufficient in 99.999% of all lawsuits.5.