Hi Saibaba,
I do quite like Pascoe Vale, however as Aaron said, the prices really reflect the quality of the suburb.
I think that Glenroy has been taken over by developers, creating a huge over-supply of units. A quick search on realestate.com.au will show just how many units are for sale at the moment. From memory, the 'standard' block size of potential unit sites are around the 700sqm mark. However you really need to keep in mind that it may take time or a lowering of prices in order to sell the finished product. Although I don't think its a bad area for developers, I think that there are better suburbs to look at nearby that may provide a better profit.
Perhaps consider Lalor, Epping and Thomastown as well. The council have some big plans coming up and are very pro-development as a result.
Selinarra