ADUs and their income potential are a hot trend right now in real estate investing and as usual, the conventional lenders (FHA etc) are going to be slower to adapt

This entails furnishing bank statements reflecting ample cash reserves to cover the property purchase and potential rehabilitation costs to get the project started.

I have been preapproved and have been touring potential houses.

You will meet people in your area that you can potentially partner with.

the property was tired, needed revitalizing and had huge upside equity & income potential How did you find this deal and how did you negotiate it?

The 401k can accept rollovers from any other qualified retirement plan except the Roth IRA (for now, there is proposed legislation so that this restriction may be removed in the future). 

Calculating the potential cash flow and ROI by considering the property purchase price, rental income, expenses, and potential appreciation is key.When looking for a property to invest in, it's important to consider the potential rental income it can generate.

The earlier you start in your RE journey, the better off you will be in the future.

Analyze local market trends, rental demand, and economic indicators to pinpoint growth potential, and reach out to local investors / RE professionals in your area.

Maybe in the future we can connect so I can learn a little more.