This is difficult to answer because you haven't given us much to go on. What type of hardware are they building, and how big and fast do they plan to grow? It really doesn't sound like they have a growth strategy in place yet, so my guess is you would need to create that for them, right? If that is the case, then you would need to show them how you have helped others in similar situations do the same. When I was trying to land a multi-million dollar client, I had to show how I had already helped a similar client do the same thing they were attempting. If you have that experience, then you can justify by saying, "They paid me X for that service. I know that may be high for your budget (and it should be), but maybe there is a way to work on my salary and also offer something else to compensate for that?" This gives them a framework to start from, and opens the door to equity conversations. It also puts the ball back in their court, but with a little guidance. Most importantly though, don't settle if you don't think you will enjoy the job or career. If you know what it will take to keep you engaged and happy, set that as your stop-limit and don't go lower unless the upside potential is worth it.

Yes, you will. Be sure you calculate your office space as a percentage of your total home square footage. You need to be sure you also use your office space only for work. I have had clients and friends who have had "surprise" IRS audits to verify that the home office was really only used for work. Your personal tax return doesn't need to list your business' mailing address, so they won't question the difference in mailing vs. physical address.

Investments aren't taxable. You need to make sure you have proper documentation from your investors showing either their membership interest (LLC), shares (C or S Corp), or other article of organization showing their ownership interest in some way. You are required to pay taxes on revenues earned, but in many cases you aren't required to pay unless you cross a certain threshold. Each state has its own laws, and you can search "Department of Revenue for [STATE]" in Google and find the best way to record your revenue and taxes. Once you get enough revenue, hire a firm like ADP to do your payroll processing and also set up the corporate tax payments through them. This makes things easier, but does cost money. Since you didn't mention how your entity is set up or where you are doing business, it is hard to give specifics.

Don't focus on the features of what you do. In your question you describe a lot of features that don't really address the emotional aspects of what your target wants. Instead, focus on the outcome. If they are struggling, then they definitely have these insecurities, even if they don't openly admit it. The thought in their mind is "If I could only overcome _______, then my life would look like _________." Fill in those blanks and you will be onto something. For example, "If I could only stop eating so much junk, then I would finally feel secure enough to ask that hot guy to go get coffee with me." Most people won't admit they have a problem, but everyone yearns for a better version of themselves and their life. Touch on that in your message (and test using social media, email, surveys, etc.), and you will be off to a good start.