I've ran some simulations and the properties are showing negative cashflow (-1% -2%) for the first 3 years, but then after year 3, things start to go back up with positive cashflow.I wonder if it make sense to take this risk, buy the home (with 20% down), maybe refinance later on (considering that the rates will go down) and eventually improve the cashflow?

Eventually you would want to pay off the balance or refinance your existing loan to pay it off. 

My goal was to eventually do a whole new kitchen anyway.

If you rinse and repeat, doing this over and over, eventually you will see you have the knowledge yourself.

Saving up more money over the years and scale slowly with 2 to 4 units and then sell eventually to buy something bigger? 

Then, you can start with renting out rooms and eventually moving out and having 1 cash flowing property.

Buy all multi-family properties via mortgage w/20% down payment + deal w/the terrible interest rates, and hope to eventually be able to refinance at a lower late?

You can do this by working at a mortgage company, title company, wholesaler company, real estate brokerage, OR if those things don’t seem practical you can do it vicariously by making friends with investors buying and selling multiple times a month, getting to know them, and eventually they might take you to the closing table, and to walk property when they buy.  

-find a good Realtor in your area who is willing to verify your numbers or point out what you did wrong…even if you are buying off market, a good Realtor who understands investing won’t take that personal and will probably be willing to help you ** IF ** you are planning to eventually do business with him or her.  

Then you eventually get good enough to support a family and you don't have any exhausting corporate ladder determining your income and future.