I’d also like to know what type of timeline were you planning to achieve the completion of the deal by?

I'm planning to post the ADU in Airbnb, FF, and Zillow.

I have a property under contract, that my GF and I are planning to house hack then rent out entirely after a year or 2.

What is the most difficult step along the journey from "I've got capital, a strategy and a plan" to "I found the perfect deal"?

I go into a multifamily assuming it won't be cash flow heavy for 6-12 months until you finalize your business plan and get it stabalized. 

There are over 20+ enlisted CPAs here in Biggerpockets assisting Real Estate investors with their tax planning and accounting.

I've been trying to strategize and plan ahead regarding my investments and managing my portfolio.

We purchased this directly from the seller at an incredible basis and look forward to executing our business plan in the coming years.

It was our plan to flip, flip, flip…use cash to buy a keeper.  

These numbers should be determined using a combination of the historical financial data available, feedback from your property management company, your business plan, and the property characteristics.Generally, you can expect per unit numbers like this:Repairs & Maintenance: $200 – $500 per unitAdministrative: $150 – $350 per unitUnit Turnover: $200 – $300 per unitContract Services: $200 – $500 per unitUtilities: $800 – $1,200 per unitAdvertising $100 – $300 per unitPayroll $1,000 – $1,600 per unit (very market specific)Insurance: (very market specific)RE Taxes: (very county specific)Again, these are very general per unit numbers but they should help provide you with guidance.