Most are 18 month max you may not leave enough time to finish the build or have to worry about doing 1 or multiple extensions. 

(There are exceptions on number but not time, but this best/easiest.) then you have another 135 days to finish buying the replacement.

I finished reading long distance real estate which was very helpful in showing that it is feasible to buy properties out of state. 

I'm refinancing a 8 unit apartment, I'm trying to add a HELCO after finishing refi. but all the lenders doesn't all second lien, is this normal?

It is definitely doable to close a deal before you finish your studies.

From it raining a lot the night before the property going active which brought to light foundation issues hidden behind the pre-existing finished basement paneling.

What's my return if the house costs $X I have to put Y% down, and pay $Z to finish the rehab?"

Ascertain your investing budget, evaluate your level of risk tolerance, and set attainable financial objectives.Carry out in-depth market research on the fields that interest you.

No...different house....the more expensive one is different quality...all brick, different finishes, different appliances, different lot size, 30 year shingle vs 20 year shingle and so many other details.Dallas vs Collin County....two very very different places......take places like Frisco for example where most homes have been built in the last 20 years vs Dallas where very few homes have been built in the last 20 years. 

Generally will want to see fully finished/turnkey to get a 30-year option like DSCR high credit or not.If you can get the first property completed and leased up and at least get the credit for yourself back up in the 650s pretty quickly then a DSCR Loan should be possible on that one - that can be the first step