Looking for input on the following 2 issues. 
1)Real Estate owned by two people each with 50% interest. What options
does each owner have/not have for selling etc? Absent any special
agreements, can someone force a sale? Is there a 1st right of refusal
for any sale? What if there is a mortgage and the 2 owners personally
pay the mortgage and one owner fails to pay? Is there any difference
if the tenant of the property is a business owned by the 2 co-owners
of the Real estate (esp if one owns 75% as below in (2).
2)a closely held corporation with 2 stock owners one with 75% of the
stock, the other with 25% of the stock. What rights does the minority
shareholder have? What rights to books, records and decisions? What
benefits does the 25% owner have? 25% owner will reap proceeds if the
business is sold, but, given the unlikelhood of any dividends, what
benefits before that? Why would anyone want to buy a 25% stake in a
closely held Co if there is no dividend requirement/ promise.

I am giving my views on both of your questions:-

1) Real estate owned by 2 people with equal shareholding are not very
common because of its very nature of differences which can arise. But
if it is that 2 persons each of which holds 50% in a real estate then
normally one cannot sell the real estate without the conscent of the
other partner and signature. But in abnormal circumstances one person
has a legal right to sell only his 50% holding even without his
partner conscent, provided the real estate is equally divided in terms
of value before doing so. For e.g. similar length of road-front to the
property.
Yes there is a first right of refusal if the real estate was not
equally divided in terms of valuation. With the help and in presence
of legal counsel one can divide the property. If one of the owner
doesnt pay the martgage both of the partner will be responsible to pay
if the papers are not very clear.

2) 25% shareholding means he is the owner of 25% assests of the
company be it machines, land, reserve or dividends etc. Though in real
75% shareholder can take most of the decisions with his own but all
the share holder who has more then 15% shareholding has a right to
vote in the board meeting. Hence if he found any irregularity he can
easily take a legal action. 25% owner benefit is that the value of
business generally increasing over a period of time which is much more
then a return from bank or even say other investments. Hence in future
say after 1,2 or 4,5 years he can sell his 25 % stake for higher
valuation sometimes 10 times of 100 times if the business works.
But if the business scope if not so much attractive then selling 25%
stake by the initial partner is not an easy task as u said there is
not much chance of dividend as such.
Some times Banks and Financial institutions buy such stakes if you proceed to them.

Good Luck and Take Care,
Kindly write to me for more information.