Obviously we can't tell you more until you post the link, but let me give you some general advice.

If you need to really scrounge together the cash to pay for the E30 then you shouldn't buy it. These are old cars, and most of them are home to components which are well past their use-by date, and may just be hanging on by a thread. There's a good chance you will have to buy some replacement parts in the first year or two of E30 ownership. Some E30 parts are surprisingly expensive unless you can source decent refurbished/aftermarket examples, so if you're blowing your bank just getting your hands on the car then you might end up in trouble.

You will also have to do your research when sourcing parts because a lot of aftermarket suppliers of E30 parts have problems with quality control (i.e. their products are total shit). Sometimes there might not be much feedback available for a particular part, and you'll decide to take a gamble on an aftermarket option (usually because it's significantly cheaper than OEM) only to find out that it's low quality or defective. This can be a costly mistake, particularly if the seller is uncooperative.

The cost of parts is compounded if you're not capable of working on the car yourself (required skill and necessary tools are the two key factors here) and have to pay someone to do it. This is something you can learn to do yourself, as everyone starts somewhere and you learn through experience. The problem is that you're planning on using this car as your daily, so if it's out of action while you're teaching yourself how to fix it then you'll be relying on public transport or friends/family to get around until you complete the work.

Don't let all that turn you off buying an E30; they're an excellent car and a lot of fun if you take good care of them. You just need to understand that it's not always going to be a smooth ride if it's to be your only car. Vigilant maintenance goes a long way, but no matter how careful you are there's still a good chance you're going to be contending with the issue of perishing components. You need to be prepared to either blow some cash or spend the time teaching yourself how to work on the car, and carefully sourcing well-priced parts and tools.

If I were spending ~5k on an E30, personally, I would want another 2k kept aside to help me keep it on the road long enough to get a feel for what needs work and address whatever issues arise in the short term.