All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
In principle, real estate valuation is a permissible business since it is about offering a benefit against a wage. Moreover, a real estate valuer should be honest and trustworthy since Allah, The Almighty, said, "O ye who believe! Fear God and be with those who are true (in word and deed)"{At-Tawbah, 119}.
Parties with whom the real estate valuer deals vary according to the nature of their business; It could be a bank, an organization or else. However, the nature of those parties` business doesn`t affect the work of a real estate valuer since, in principle, it is permissible. In fact, He/she estimates the price of a certain real estate regardless of the party asking for that service, and this doesn`t help in committing Riba(Usury/interest) for Allah, The Exalted, said, "Help ye one another in righteousness and piety, but help ye not one another in sin and rancour: fear Allah. for Allah is strict in punishment."{Al-Mai`da, 2}. In addition, real estate valuation is a lawful job.
Accordingly, offering real estate valuation services is permissible regardless of the party/client asking for that service. And Allah knows best.