Contamination can be any size, such as a heating oil tank to a gas station/small oil company.Im aware of compaction issues, so in some cases building construction could not happen although there are other uses for such land.

I am not certain, because SDIRAs have different rules than solo 401k plans, but you may be able to partner with your SDIRA, as long as EVERYTHING is done in direct proportions.

My houses have much lower replacement cost so I don't know if insurance is proportional and thus comparable.

If you can absorb a potential large loss and are willing to put more money (yours or an investors who's also willing to take on a similar risk profile) on the line, then you can reevaluate.The draw of the larger investments is obviously the beefed up income statement, but ignoring the proportional increase in risk (only magnified by the level of leverage you place on the property) will set you up for a hard lesson.

I think you get more value studying another area you are interested in, which will give you a backup plan, and then study/work in REI in your own time.I wonder the proportion of successful BiggerPockets investors (ie, made $1 million+ in real estate) studied real estate in college? 

The front yard had no grass growing in it the ground was so compacted it was harder than the concrete driveway.We encountered some unexpected things in the process, and the fact that it still worked out just shows that we got lucky since I didn’t have any idea how to estimate rehabs.

@Nat Chan , as you've no doubt learned, many people in this country lose all sense of proportion and perspective when they hear words like "food stamps".

In all my years of construction bad ground is bad ground and you have to keep excavating until you hit solid earth then backfill in compacted layers.

@Dave Meadows Thank you for the information.So is the amount of PMI I pay inversely proportional to the % down payment I make?

You should be more concerned with cashflow than with what proportion the taxes represent of your expenses.