For heating I like to have an intake at the lowest part of the house to pull out the cold air. This may very well be in or near that crawlspace. If it has a filter, then I wouldn't worry about dust. Just be sure you're replacing the filter regularly. However, I would want to know how fresh air gets into that crawlspace. If it's sealed off, then you are hurting the performance of your heating system. Otherwise, your intake is effectively where ever the opening to the crawlspace is.
When possible, it's nice to have a short path between the return vent and the blower unit. In addition to less cost of materials, you have less distance you are forcing the blower to suck the air through, and therefore more efficiency.
According to Chicago Building Code
18-28-504.1 Installation.
Clothes dryers shall be exhausted in accordance with the
manufacturer’s instructions. Dryer exhaust systems shall be
independent of all other systems and shall convey the moisture and any
products of combustion to the outside of the building.
Exception: Where the make and model of an electric dryer is known
and the manufacturer’s installation instructions do not require
exhaust, see Article 4, Ventilation for room exhaust requirements.
Venting a dryer inside is a potential fire and mold hazard, and can negatively affect indoor air quality causing sickness (and/or death, maybe).
You should bring this up with the condo association, the building owner, and potentially the building inspector. A possible down side to this action is, the condo association could ban the installation of dryers altogether. So you'll want to try and suggest some alternatives.
I'm going to guess, the condo association is worried about the appearance of vents sicking out all over the building. A potential appeasement would be to select a nice looking vent (voted on by the condo association), and force anybody who installs a dryer to use the same vent.
They may also want all vents to be installed in similar locations, so the vents are uniformly placed on the building. A good way to insure this would be to install all the vents at once, including installing vents for units without dryers (in which case they should be sealed until in use).
Best Answer
Dryer vent air is full of water vapor and dust. I wouldn't want to blow it into my house.
I do not know how much heat (BTU's) a dryer outputs during a run but it seems like it would be a small amount, and of course most people don't run their dryer very often - maybe a handful of times a week.