Why is investing in metropolitan downtown like SD or LA a bad idea?

I am in the Old Town area, very close to downtown, my rent is $1260 per month and includes most utilities and even parking.

I'm currently looking at my first deal which is a very large duplex in the downtown area where I live. 

This home is a 20-minute train ride to downtown San Francisco, although some corporate rental companies only have units downtown.Tyler - What kinds of areas would you typically target for a 30+ day VR?

In Fresno i'd stick to downtown or tower district, they tend to have the best rental markets for the area as far as caps and quality of tenants. 

Looking for security system recommendations for a 35 unit apartment building in downtown KC.

I am new to real estate investing and I would like to purchase my first multifamily property in the downtown Sacramento area. 

I honestly feel the property is worth in the 150 range, it is located in a historic part of downtown in my city, where property value is rising, and there are in the process of building a new medical school 2-3 blocks from this location.A - 1/1 - lease from 6/12/2017 - $525B - 2/1 - vacantC - 1/1 $525 lease from 6/16/2017D - 1/1 $425 lease from 11/12/2010 - these tenants are likely to live in the unit until they pass away.

Coral Gables, Coconut Grove, Shenandoah, South Miami, are great neighborhoods closer to downtown, Brickel and Miami Beach and traffic is not bad in these areas.

I run The Spokane REI Group here in downtown Spokane.We're a no sales, education oriented network group.