I'm kind of picky about what I allow though and I have strict pet rules in hopes of turning careless owners away.

I know the actual cost can vary by location, property type, and provider, but I'm wondering if anyone has a solid set of rule of thumb they use when crunching numbers for a quick analysis?

But, it’s worth consulting with a tax professional to assess whether any parts of the expense could still qualify for immediate expensing under safe harbor rules or another method to maximize deductions. 

The fha 100 mile rule will be triggered whenever you try to vacate your current primary and also trying to use the rental income to qualify.However, this 100 mile rule can be exempted for the following rulesRelocationIncrease in family sizeVacating a joint owned propertyNon-occupying co-borrowerIf you are not trying to use FHA on your 2nd house hack, you can use conventional and the rules that I mentioned above will not be a concern and will be exempted.

I've been trying to find a definitive ruling on the subject for MD, but it seems there are just general usury guidelines that a landlord SHOULD follow.

They apply their house rules to the guests so you aren't stuck trying to evict one that relapsed.   

Since this is a capital improvement, it doesn't follow the same rules as a standard expense, so you'd likely start depreciation in 2023.

There are rules to follow!

The rule I use is to double the money after five years in case you need to sell.Meaning, with your initial investment of 132k (down payment plus initial closing costs), and considering an additional 5% closing fee of the home’s value when you sell (roughly another 30k for agent and lawyer fees), your total upfront cost plus closing on sale would be around 162k.

There are rules to follow!