Read and understand
Always, always, always read everything in the employee package that you are handed when you are officially offered a job. If you are going to relocate, make sure you get the paperwork in advance and take the time to go through it before you start canceling your lease or putting your home up for sale. Never sign anything at an HR office other than a receipt for items you are given (passes, codes, keys, etc). It's a classic move to pressured into signing a stack of complicated documents that are thinly described verbally as being "standard, everybody gets these and we need them before anything else can go forward".
If relocation money is an expense account rather than a lump sum, find out what the restrictions are. Since a lease deposit is cash held in escrow, it's not tax deductible for the company so it makes sense that they won't allow that. If you know that you will need money for a deposit, try to get a "Signing Bonus" that will cover it and let them decrement the relocation allocation in kind.
I've always done a bunch of research into the cost of living of an area before I accept a job. One may find that it's commonplace to have to pay a lot extra for a parking space in addition to the stated rent of a flat. You may also have to get a city permit to park a car on the street without having to pay high prices at meters. Flats might typically come furnished or may not which could be different than where you were living before. Don't take anything for granted. I've never moved to a new country, but I can imagine that language skills would be a big factor even in a larger city when dealing with bureaucracies.
Since the job had a probationary period, there was no guarantee that they would have made it permanent even if HR wasn't working so hard to ruin somebody's life from day one. This means that it would have been doubly important to make sure the relocation money was not due to be paid back. You also wouldn't want to sign a year lease on a flat or make other long term commitments. Keeping a back up plan is a good idea to so you can move back to where you have family/friends and a network to get another job quick in the case things don't work out. A local storage locker would be good to stash anything that probably won't be needed for the duration of the probation. Wait until your are firmly established before brining it along. Make sure you relocation offer will allow that.
Never be blinded by a job for a prestigious firm or a large paycheck. Take a deep breath, read the fine print and figure out what you will do if everything goes down the crapper.