@Hsin-I Hsu  It depends on your long term goals, risk tolerance and earning potential.A couple of bay area sayings:   Any time you can afford to buy real estate you should.  

It all depends on the situation.

Depending on what type of investor you are or want to be, there are still deals out there.

Midnight drunken brawls happen, but are more infrequent then you might guess depending on your screening. 

Another thing to consider, most single family bedrooms rent for 800-1200 monthly depending on the area.

Just depends on your current rate, strategy, future cash-flow, etc. 

Depending on the lender and program your biggest hurdles might be credit score and income and time in job. 

For a nice possibly furnished STR, you are looking at between $250,000 to $350,000 depending on your budget. 

Depending on market, I would plan to invest 100k in a single family home, find a good property manager, realtor, attorney in compelling market and just start. 

Some of my clients love the cash flow in the east side neighborhoods over by Slavic Village and Broadway selling between 90-110k with rents up to $1,800+, but just really depends on the types of neighborhoods you're investing in and your risk / reward threshold.