On more complex septic systems, you can be in the $100,000+ range or higher depending on how many units the single system serves.In addition to the above, the regulatory environment is a moving scale.  

Once I had figured out the business model, I bought a few small properties to understand the scaling costs.

I'd say 30 days.....but of course depends on what rent you want, what time of year, where the property is, what price range and so many factors.Typically I say Summer rents better than Winter, especially in great school districts.If you're above probably $3000/month in rent might take 60-90 days and maybe longer depending on how far up the price scale you go....Probably $1500/month and less in metroplex, might be a week or two.Homes that allow pets seem to rent faster than those that don't....so could depend on where you are there.Seems like the last few I've rented went pretty fast if the condition was good and the rent was right....people wanting to apply and move in a few days.Some post said try Z....and I would say just the opposite....typically I get the worst applications from there, but maybe it depends on how picky you want to be.So typically your first payment is about 1month after you close. 

I do think you can make a living of liens but it requires to do it on a larger scale.

Just because you are approached on some deal and you think it's an opportunity isn't enough, you need the resources and knowledge to take charge.See an attorney who has put small partnerships for manufacturing ventures together.

There is more work, which is as Brian pointed out a sort of economy of scale.

It's all about scaling those small profits up... ask Walmart.

They mainly seem to be more 10,000 foot view and how they got there or managerial/scaling tips.

This would allow you to establish a relationship with a HML too, so you can open up other options as you scale.

I'm trying to get a feel for recognizing this in both a micro and macro scale.