That is very hard decision and can be debated to both sides.
Our history says, Maharaja Ranjit Singh and others donated many acres of land to the GURDWARAS. Diamonds and Gold were also part of offerings to GURDWARA SAHIBS.
ARGUMENT FOR "INVESTMENT"How those offerings were utilized, then? Most probably, land was cultivated or given on lease? That income comes to GURDWARAS again (i.e. NANKANA SAHIB, PAKISTAN). Markets built on those lands, when given on rent, are used as source of income to the managements (i.e. SGPC, DGPC).
Share or Stock Market, is the modern way of keeping the money, in investment. As the land or the building is leased or rented, so the money is wisely invested, in so called Share Market.
If Share Market is OK for Gursikhs, why not for GURDWARAS ? (I think, SHARE MARKET as business for Gursikhs was debated on this or some other forum, earlier)
ARGUMENTS AGAINST "INVESTMENT"Money, if not utilized immediately, for most desired situations, is not ACCEPTABLE, in principle. It is not the money, which is important, it is the UTILIZATION and FEELING related with money, which is more important. As Sukhdeep Singh VEER Ji says, GURDWARAS are not buiness houses. What is a loss, for a Business House, could be a Gain, for Guru Ghar. SACHA SAUDA is defined by "Using the Money for Welfare of Humanity'. There are always enough of resaons to use the money. Schools, Libraries, Play Grounds, Free Rest Houses, Gyms, Hospitals, Free Kitchens etc etc, all are better investments, with current and immediate use of money. Money invested in humanity, is better than saved for future.
A sikh has always to chose between, MATERIALISM AND SPIRITULISM.