Buying a new instrument can be exciting, but it can also involve a significant expenditure. Here are some of the common mistakes people make when buying an instrument.

1. Damage. This is common with used instruments. Wood instruments, such as violins and guitars, can have cracks, separating seams, and worm damage. Pianos can have cracks in the soundboard. Organs can have rotted bellows. Brass instruments can have dented or corroded tuning slides. This isn’t always obvious, and for a significant investment, it is worth paying an independent repair technician to analyze it, so that you know what you’re getting into. Some of these issues can be easily fixed, but others indicate that the instrument is essentially a lost cause, or is diminished to the point where it shouldn’t be in professional use. A subtle form of damage is in the wiring of electronic instruments. Used ones may have intermittent problems. So, put the instrument through its paces. Look it over carefully for signs of damage. Try every note and feature. Listen carefully for any inconsistency in sound across the range, and for random rattles or buzzes. It might be a sign that something’s up.
    

1. Wrong size. Often, an instrument seller will demonstrate the quality of an instrument by playing it himself. This doesn’t really help you, much. Different instruments are sized to different size humans, and you need to find something that feels good to you. Similarly, the weight of an instrument is worth considering. Some instruments are so heavy, you may need to play them sitting down. This is an often overlooked aspect of choosing an instrument, and one of the ways trying it out in the excitement of a music store might not translate well to actually performing with it for three hours a night, on stage. Always try an instrument before you buy it, unless you are absolutely certain you know what you’re doing. Its feel in your hand is as important as its sound. You have to love it.
    
2. Getting junk. Our budgets often force us to get instruments that aren’t good enough, and we often regret it. Spend as much as you can afford. It often makes sense to get a better quality used instrument than a lesser quality new instrument. Low-end instruments often have lesser sounds, and will therefore make you seem like a worse player. They might be unpleasant to play, in some ways, and may fall apart more quickly than better instruments.
    

1. Getting obsolete technology. Some old instruments are delightful, but in other cases, advances in technology have really improved instruments over their ancestors. MIDI instruments are getting better and better, and the vintage ones are rarely preferable to most people than the new ones. Pianos of different vintages have their issues; some manufacturers have gone through periods of using better or worse parts, and so there are some models to be avoided. Brass instruments of the early 1900s are harder to play and generally more problematic than current instruments. Acoustic bass pickups have improved dramatically over the past couple decades. Materials have evolved, particularly metals, plastic, and electronics, and newer instruments often out-perform their predecessors. So, sure, buy an old Strad or two. But older doesn't always mean better. You might find a gem, but do your homework first.
    
2. Choosing looks over sound. Usually, how an instrument feels and sounds are the top priorities. How it looks can be deceiving. That said, you should generally like how it looks, as you’re going to be spending a lot of time together! Just make sure that’s not your primary motivation.
    
3. Giving up too soon on your current instrument. Consider potential modifications to your instrument, before replacing it. Changing the action, removing the whammy bar, changing the strings, buying a new mouthpiece, having it refinished, or repairing a dent might give your current ax a new lease on life. If your current ax is a beloved old friend and you really don't want to say good-bye, find a good repair tech, and ask him or her what the possibilities are.
    

I didn’t list over-spending. In some cases, musicians do get into financial trouble because of their gear-buying habit. Some instruments are over-priced, and some sellers try to rip off their customers. Usually, though, people are more or less fair, and musicians don’t regret spending significant money for a quality product. The expenditure generally hurts for a very little while, and then we forget about it. But if you’re in a financial hole, obviously, this will just make matters worse. Particularly, good quality used instruments will keep much of their value, so you can always resell it.

Just remember, go for feel and sound. Walk away from it, and come back if it calls to you. Put the prospect through its paces, before you buy it. Don’t just play your favorite piece. Try every note and feature, at every dynamic level. That will help you choose a new instrument that will feel like a true extension of your voice, and lead you to a purchase you won’t regret.