Bicycle hire in Sapporo

I'm visiting Sapporo for a month in June to do a course.
I can take a train from my hotel to Sapporo station, but to save money, I was thinking of hiring a bicycle.

I searched online and found Porocle. it's an okay idea, but I'm worried if I take the bike somewhere far away to anther Porocle rack, someone will take that bike and then I'll have no bike!
So I was thinking maybe I will hire a bike per day.

Does anyone have experience with riding a bicycle in Sapporo?
Are there places I shouldn't park the bicycle? like Sapporo station is a bad place?
Do I need to lock the bicycle?

Buy used one.

No such long days rent(rent a cycle).

If I buy a use what and use it for a month. What do I do with the bike afterwards?
Can I leave it somewhere or try and re-sell it?