I was really frustrated by this as well. What I found most useful was to zoom in and see how much space there is available on each street. I also hide all of the decorations because it makes it easier to see the available spaces. Just click the decorations icon on the street bar and it will hide them on all the streets and platform. You can figure out the available spaces for each street on the street bar. it shows as: ###/### where the first number tells you how many spaces are used on that street and the second is the total number of spaces the street has. Then if you select the building the streets will show you where the open spaces are by having yellow lines under each open space. Even more helpful is that the spaces will change to red if the item you are trying to build is too big for the space between the buildings already there. So you can move the building around across each street and between streets until you find the correct space.
I did not have to take any buildings away in order to have enough space. It's there, you just need to look a bit.
