There are a few ways you can approach this, but given that you are taking over this house with a fair amount of equity already built it I see one very attractive option for you:  If the true value of this house is $450k you can do what's called a 'gift of equity' with your father, and essentially borrow the full $350k that you need to actually buy it for him.  

Which do my fellow BP members think are more attractive to investors?

Better clientele will be attracted to the neighborhood, you can raise your rents, and the building increases in value dramatically.

Do they SOUND like something that will attract people to look?

Walk to work is appealing to small business owners.The stream/ park could be attractive for fancy shops or restaurants.

JUST MAKE SURE YOU ARE PAYING FOR THE MATERIALS YOURSELF OUTOF YOUR OWN ACCOUNT/WALLET HOWEVER LOGISTICALY YOU HANDLE THAT (AND ALSO AVOID AT THE SAME TIME A CONTRACTORS 15% TYPICAL MARK UP).

Not once do I recall the property being occupied with actual tenants, willing to produce a valid lease agreement, at market rate or otherwise.I would say if there's going to be an increase in difficulty, it will be due to the investors willing to pay 80 cents on the dollar, or the GSEs bulk programs taking off and causing servicers not to lower opening bids to attractive levels.

Storage looks attractive in the future.

If market is really $1,200, then surely $1,099 would attract good tenants.

IRRs are also driven by alternative investments (stocks, bonds, savings rates) as the projected returns on these investments decrease, so does the IRR required to attract capital to your deal.My experience (I am a buy & hold syndicator, still waiting on the right deal for my first flip), investors today expect 15% minimum IRR (low risk.)