How to get my parents on board with another guitar?

Quite entertaining stuff this - people calling a steel string guitar acoustic and forgetting that a classical/nylon string is just as much an acoustic guitar. Here goes: There are basically two types of acoustic guitars; classical/nylon string guitars and steel string guitars, some times referred to as flat top or western guitars. You may argue that resonator guitars are a third type ... but enough of this already.

Now to your question. Since we don't know your parents, it is not possible to tell you how you should best present the case. In any case; if you look at it from their perspective, then you will understand if they'd argue that you are more than well stocked with guitars.

Personally, I can totally relate to your G.A.S (gear acquisition syndrome) since I've got guitars by the truck load. But I'm a grown man and I simply buy one if I have the money and I want to have it. Since you're living with your parents, you will need some goodwill - take it or leave it.

If one of your guitars is a hard tail (non tremolo) bridge, then it really isn't that much wear and tear to tune up and down a half step, say between B and C. Yes, you will get a little more wear on the strings and probably nut over time but nothing major. A graphite nut material may wear down somewhat faster though.

Another option could be to get hold of a Morpheus Drop Tune pedal. These are more than adequate for rehearsal or practice. They may possibly not cut it in a live playing situation but are more than fine for home practice. If you use the pedal to drop half a step you should have no issues what so ever.

https://www.youtube.com/watch?v=_Mf54MxqUaA

The new Digitech whammy pedal have a similar functionality:

https://www.youtube.com/watch?v=V2SOZBtOF2U

I've whittled my collection down to 4 simply because I don't need or play 18 guitars anymore, I keep one electric because its just rare and custom built, another acoustic because it sounds so good and the company is no longer in business, the other electric and acoustic are still available and I have no problem playing the crap out of them, Then the fact with the help of a Roland GR-55 guitar synth which both are equipped for alternate tuning is as easy as hitting a foot switch and changing patches, and with an infinite number of ways to change over 900 patches versatility is a non issue, So in other words one guitar can literally sound like anything you want it to in any tuning, Although some synth settings like pianos the tracking is a bit off and takes a steady hand and light touch to sound proper, But in the end once figured out and mastered will make you a better player with no limitations as to what you can do with a guitar and the sound it makes,

@H2SO4: Because they are two different guitar maybe? they have a different label for a reason.

If it is with your own money I dont see the problem. As someone else said, get hangs and put them on the wall, if not get a guitar stand for multiple guitars. They might complain that you are getting too many guitars but it is for a reason. I also have 5 guitars, an acoustic, classical, Ibanez GRG, Squier Strat amd epiphone SG special.

Good luck with that. I only have 2 and I can't get my parents to let me buy another. Maybe keep them in your room?

P.S. If you do get another one, hang them in your room with wall hangers. Guitars are works of art.

Get your own money and buy it yourself, you're 17. Learn to be independent.

Why would your parents care about your guitars?