Maybe you need to find a money partner or a bunch of friends that are willing to go in together to limit the losses or maybe even just pay cash depending on the friends.   

$822.375 is high balance loan limit for you with that score you should be able to do a STAND ALONE HELOC. 

Probably not, but it may very well be just my limited experience on the matter.As @Zorya Belanger states, you get what you pay for.

So, is your debt servicing capability limited? 

I am financing a rehab on a new quadplex, and wondering the best Credit Card to get/apply for with no APR for 6-18 months and pretty lenient with credit limits.

Based on your income, it'll tell you what your max house price should be, and I think this calculator uses 28% of Gross Income as the max recommended limit.

Investment interest is limited but potentially deductible2) What if I use the cash to purchase upgrades for another investment property - can I write off both the cost of the upgrade AND the portion of interest associated with the upgrade? 

As well as there can only be an increase of rent once every 12 months that is limited to inflation rate of that year + 2% (approximately 5-6% - 1200 rent could only be increased to 1275 when similar properties around the area are going for 1400-1600)

Additionally, is there a limit to the number of people attending the bootcamp?

I've read here that they aren't but reading the city's webpage seems to indicate that they may be allowed depending on what "zone" it's in, and some limit on number of STRs per development??