Work your way from top to bottom first with your plan, start backwards, think of your goals and how to get there, look at specific strategy vehicles to get you there, learn them, and find ways to start applying them in real life.

Also, some vehicle expenses.What about computers, printers, etc?

Thoughts on the best vehicles to pull equity out while keeping the owned properties in a good cash flow position.

In the upper left under vehicle storage, select either Boat or RV storage, doesn't matter.

Thousands of homes in TX, LA, & FL are dealing with flood damage right now that are not in flood zones.Workers Compensation coverage if you have anyone on payroll, any subcontractors that do not have their own coverage, or if you have any Statutory employees (most common would be realtors).Business Auto may be needed depending on the ownership, size, type, and use of the vehicles used to service the properties.Equipment coverage may be needed if you have Tools and Equipment you use to maintain the property such as Tractors, Bobcats, power washers, generators, etc.Builders Risk policy could be needed if you are renovating a property before renting it out.Hope this helps with some possible policies you may need.  

And no one will have any idea who's trash or unlicensed and broken down vehicle is in the garage.A better plan is (depending on your market) try to locate professionals, or grad students that are looking to share a large rental with nice finishes and amenities.

Why not use a HELOC when the time comes as the vehicle to pull out additional cash for the down payment on the next property? 

Majority of people use it as an investment vehicle, OP.

Tenant responsibilities, payment due dates and allowable methods, late charges, the "joint and several" clause, adding/removing someone from the Agreement, yard maintenance expectations (which are also spelled out in the Agreement), vehicle requirements, etc. etc.

If you're okay with that, and taking the long view, then yeah, you'll have a hard time getting into an equivalent investment vehicle for less money down.But less money down isn't always a good thing, especially depending on what you're buying.There are many reasons why moving up to larger multifamily properties makes sense, but one I'll point out here that's worth considering lies in how properties are valued.Your quad is based on comparables, which means it's worth pretty much exactly what all the other similar quads in the area of your property are worth.