Next, you must decide if any expenses associated with renting out the property are deductible or not.

@Martin Guerrero although you can (and often should) bring a GC with you (esp. if you plan to do a rehab), if you want to become a successful RE investor, you should make it a goal to become proficient at evaluating properties (meaning: evaluating problems with the property, likely costs to remediate problems, potential value add opportunities & associated costs, etc.).Ultimately, you want to become almost as good (or maybe even better) at evaluating properties as a GC and inspector.   ...Once you get to that level, you become an invaluable piece of your due diligence process, and your due diligence process involves three experienced pros (you, your GC, AND your inspector--which is much better than just a GC and inspector).  ...at that point, your due diligence process is multi-faceted and very robust (which is critical to success in RE investing)....you can make your due diligence process even more robust by adding an agent who is highly experienced in property rehabs, RE investing, and who understands how to evaluate properties.Good luck out there!

Can an IL Broker work for themselves or do they need to be associated/sponsored by a Managing Broker?

I find out that it is currently occupied (at the time I did research there was no indication that there was any other address associated (nothing showed up on the title pull). 

However, it's important to also consider the expenses and costs associated with operating an Airbnb, such as cleaning and maintenance, and determine if the potential income will be worth it.Personal preferences: It's also important to consider your personal preferences when deciding between a long-term rental or Airbnb.

Many associations establish a policy limiting the types of flooring that can be used, and/or requiring sound deadening material be used to limit the transmission of sounds, including "walking" loudly.

Is it comparable to LTR management where it's ~10% of gross rent/month (Average in Canada right now) What additional costs are usually associated with STR management?

Despite the difficulties that can be associated with some CA laws, it is generally easy to manage tenancy in CA if you have quality units and therefor quality tenants.

Leverage magnifies return. 3) The effort involved in adding an ADU is comparable or larger than a rehab associated with a BRRRR.

I understand looking at other areas for more reasonable prices, but I will note there are more costs associated with investments properties further away (travel costs, management costs, etc.).