Downtown is booming as well with the renaissance district going up as well as several buildings including the Chase tower being converted into apartments.  

This is directly adjacent to a neighborhood that is booming.

Some cities are more prone to boom/bust cycles than others.  

My idea is i am looking to gather more than 10 small investors like me who like to do the business in Baltimore city, and all of us buy all the properties in one street and rehab them at once, so in this case the value of the properties in that street will boom up and the small investors get their profit.

BOOM and that is how it's done!!!  

I plan to keep this property for a while, as I'm in a booming area with very limited supply just north of NYC.

And boom!

Trouble for rent collectors (landlords) and mortgage premium collectors (banks)?

Use their "value" of $200K, assume 10% for realtor fees, etc. and boom, you're making $15K per flip.  10 flips * $15K per flip is $150K in your first year!  

Boom, 1.75% more equity compared to FHA where you typically tack that 1.75% UFMIP onto the loan balance.For good credit, PMI will be a little less than half as expensive per month as FHA MI.And because it's PMI, it can drop off at 20% equity without a refinance.