Don't spend money on things you may need in the future. Buy equipment to fulfill some immediate need, if and when that need comes up. (The obvious exception is equipment that is part of your data backup strategy, because it's obviously too late to start making backups when you need them.)

That said, I recommend getting a desktop computer. Not just because desktop computers are more powerful and more ergonomic than laptops, but also because two computers are better than one. Two computers means that you can keep working when one of them breaks down. Two computers means that you can keep two “live” copies of your source code, which is an important part of a data backup strategy.

a light breeze said:
I recommend getting a desktop computer.

Seconded.

SuperVGA said:
Hopefully you're able to jump right in and develop once your equipment arrives.

No worries, I have years of experience behind my back. I'm all ready to jump and start creating my dream game! ...As soon as I finish decorating the office and buying needed equipment.

Shaarigan said:
Only get a faster PC if Unity slows down your development too much by high build/refresh stalls for example but except that, you can even run Unity on an old PC from 2007 using Windows XP!

Noted. I'm definitely going to build a high-end PC.

Shaarigan said:
Get a good keyboard and mouse is a must have regardless if you use a tower PC or Laptop.

Do you have any recommendations on which mouse/keyboard should I buy?

Shaarigan said:
I expect you to already thought of a desk and a chair to place your butt onto at least 8 hours a day/5 days a week did you?

The same question goes here : Do you have any recommendations? What chair should I buy?

@Tom Sloper PC.

@a light breeze Thanks for the advice.

It sounds like your going about this the wrong way.

Your asking what you need before you even define what your building.

As an Indie, you don't need anything more than a computer an a smart phone.

Renting office space for one person is pointless, you can just work from home. In fact, you should be working from home, if you want to claim tax deductibles', you just set a part of your house specifically for your office, and not do personal stuff in there.

Look, it sounds like your trying to get all the “things” ready. which is good. but it sounds like your focusing on all the wrong things.

Focus on what you need for the game, everything else you will just get when you need to get it.

As for stuff like chairs and mouse, and keyboard, if you don't already have comfortable ones, just search ergonomic _____________

Certainly, you should start with what you have, and if you are going to invest in something, start with a desktop computer first (if you can).

Do not try to invest in things for the distant future, I would recommend you to invest in things that will help you in the current moment, such as an "immediate investment" or an "extremely short term investment". You will start getting better at making games and keep making better titles, consequently having better equipment over time, don't worry about it now.

Try to focus on things that are essential for you and your project now.
Does it require voice/foley? Invest in a microphone (or if your phone already has a good audio quality, you can use it)

Programming?
A keyboard (it is much more comfortable than the ones already built in the laptop) and a mouse.

Just make a list with everything you and your game really need (hardware and software).

Don't think too much about office/studio stuff, think about how to improve your workflow/comfort.
If you want to think more seriously, I would recommend things like protecting the intellectual property (copyright, trademark registration, etc.) of your game, registering the name of your studio and so on.

Well, that's just my opinion. Good luck!
I really hope I didn't sound rude, kinda hard to express myself in forums without seeming rude, sorry for any misunderstanding.