One monitor is connected via VGA cabel with the VGA to DVI adapter at the end.
The problem is that I can't connect second monitor same as first one because only
one DVI port allows DVI 2 VGA dapter.
Will second monitor work if I use mini Display port to VGA adapter?
Yes it should work fine as long as you have the correct converter. I had a situation where I needed to go from DVI-D to VGA and KVMSwitchTech's ( Part # SCA-DVI-ANA) unit worked well for my application.
I guess there will be a lot of products that appear cheap. But it could be hit or miss too. I have experience about buying no name brands & they work but after a while they start flickering so I ended up buying another one. So better get it right the first time.