Should I wait for the builder to come take a look at the crack or just go ahead and seal the crack now?

There is no solid rule as per the continuous/series contracts (sure, go ahead and re-hire him, no rules after all, just risk), and it does not compute like 500 contract #1, 400 contract #2, 450 contract #3, but they will consider you are just breaking the employer law and evading the unlicensed contractor law by going just under the radar, more likely no one is going to know, but you could never tell. 

The secret of getting ahead, is getting started.It is vital you connect with a realtor anywhere in the United States, who will take the time to understand your desired type of property and areas of the market you have been looking in.Learn about the good, bad, and ugly regarding distressed properties, whether due to  property condition or the chain of title.

With careful planning and strategic decisions, real estate can indeed be a powerful vehicle for creating a legacy and achieving financial independence.

For example, did he buy a business vehicle that he depreciates on his taxes over time?

Some people take signings for $35 thinking they are making money but don't because they don't account for vehicle expenses, paper, toner, etc.After expenses, your profit only comes out to like $10/hour or so on most days because packages are upwards of 250 pages and you have to print two of them.

Those properties are likely to book up fast, and probably do already, leaving the other 90% for the rest of the guests who don't plan ahead that much. 

Its important to plan ahead on how you want to approach your first house hack investment.

Advise is to get in contact with a lender that has experience in structuring these mortgages where you can move on to the next one and plan ahead.

This lien is a superpriority lien, so it sits ahead of all mortgages and nearly all other liens (liens held by the US Government are a notable exception).