Now, there are OTHER things that you need, so if you could give more details then that would help us answer this a little more accurately.

There's no one right answer for everyone since we all have different financial situations and risk tolerances.  

If the presentation was weak, that's answers your question. 4.

But my realtor said they are going to do special assessment on this property and HOA runs badly. ( We requested HOA reserve document but no answers. ) We wanted to wait to see how special assessment going and close. 

Heads up, everyone: Dave Meyer and Henry Washington answered Alex's question during yesterday's episode of the BiggerPockets Real Estate Podcast: How to Buy Multiple Rental Properties a Year (Is It Possible?)

There’s no single right answer to every situation, but the more you educate yourself and build your network, the more confident you'll become.Lastly, don’t hesitate to ask questions here, no matter how small they seem.

This is exactly the type of answer I was hoping for.  

Hello Mike, It is nearly impossible to answer this question without taking a deep dive on the numbers of each but often times in expensive markets like Seattle the cost of construction is so high that it doesn't make sense to tear it down unless you can build something way bigger/nicer.

Quote from @Laura Stayton: It's impossible to answer this question with the information you provided...How so? 

I would bet the solution lies in your answers to those last three questions.