It’s quite appealing as a long term investment - even at today’s rates.

When you finance through national lenders, in your experience, is a balloon a common requirement for commercial loans of this nature or is it possible to get a fixed rate for 30 years?  

Tax-wise, profits are taxed at your ordinary income rate, and frequent flips may subject you to self-employment tax if classified as a dealer by the IRS.

The best place for any individual will depend on their priorities.  

This is to get your tax deduction at a higher tax rate.  

Given the lack of activity / buyers in the market at this time with rates, would you reccomend holding and renting it until the market is better to sell in? 

It's the boring places that probably won't appreciate above the rate of inflation that will provide real month to month income. 

Are there any wholesale lenders that will do a rate and term refi on 4,800,000 loan balance,  5 unit property.

While a western WA deal might not meet some Midwest cf metric like 1%, it will be above the market cap rate or below FMV of comparibles and give you options. 

You can likely do this with your savings rate (that will likely increase) and age.