@Evan Linder Congrats on getting started and willing to take some risks!
1. renting by the room. I am on your side, privacy is a huge concern. This works with college area homes, but for me, not as a house hack that I would be living in. There are many leases available online or you can have an attorney draw up specifics to your criteria and needs.
2. Orlando multi family is exactly as you say. The closer you get to the city, the more you pay, that is just the way it is in any metro area and don't hold your breathe thinking that will change. If that is really what you want, either save up and buy a decent one or suck up the commute knowing the end goal is to build wealth and there are rarely shortcuts, only sacrifices to get started!!
3. ADU- each county/city/municipality will have its own rules and allowances for this, there is no blanket answer. If you are going to stay strictly in Orange County, then focus on what they allow and don't. Be prepared for long permit times, the area is growing and that puts strains on all areas of county offices. Plan on using a GC, getting plans drawn up and likely engineers too, it won't be easy.
4. If you are house hacking and looking for easiest point of entry so that you have money to add value to the property and not use all your saving on the purchase, FHA would be the way to go. Then you move on to the next one and repeat. Unless you are a veteran and can use your VA entitlements, FHA is the route. However, the condition of the property will be important here, FHA rules are more strict than going with a conventional loan, so make sure the property is in good shape.
5. Many of the agents on here, including myself are here because we are investors ourselves. So using one of us makes sense, but still, interview and make sure they understand YOUR vision. Every investor has different experience levels, goals, timelines and so on. You understanding your goals and vision are paramount to connecting with the right agent, we are not CPA's or lawyers and don't always know what is best for you, we facilitate real estate transactions and help educate you along the way.
Hope this helps, best of luck to you!