Is it allowed to purchase a property with our primary home that has a detached ADU on the same tax lot.

I hope the property taxes go away but I don't think it is likely  talk of eliminating property tax in FLA  is that what your saying ?? 

Many investors use this “infinite leverage” approach to maximize liquidity and tax efficiency.

Bigger Pockets is a great place to find an accountant specializing in real estate taxation.A good real estate accountant can save you thousands of dollars by leveraging entity selection and formation, tax deductions, cost segregations, bonus depreciation and tax planning.I recommend finding an accountant specializing in real estate taxation, business taxation, financial planning and tax planning.Consider working with your accountant remotely to expand your options.I would also recommend looking for an accountant willing to work with you throughout the year.

(d) retained earnings from depreciation use to lower tax burden. 

Most don't understand taxes:  For example, a girl with purple hair at my credit union did not understand depreciation, and I did not get into Cost Seg with her because she really would not understand that. 

There are many tax accountants on Bigger Pockets that can help you with your situation. 

Even if we do know the exact transfer tax, we haven't seen the contract to know if the transfer taxes are being paid by the buyer or the seller or if they are being paid 50/50. 

Cash Reserves & Emergency Fund✅ Have 3-6 months’ worth of expenses (mortgage, insurance, taxes, and maintenance) saved.✅ Keep an emergency fund for unexpected repairs and vacancies.2.

There may be a property tax benefit to leaving pieces.