UPS Angel: I am sure we all want to help you but .. the variables are just that .. variable.
As Saint Jack has just said, one needs to determine whether the facility is for private or public use. Then a professional survey should be carried-out to determine the location's suitability as a heliport. In some cases obstacle clearance requirements mean that surrounding 'obstacles' may have to be removed or, if they cannot be removed, that the landing area be raised. There must be appropriately 'clear' approach and departure paths .. and a host of other regulations which although largely generic are nonetheless specific to each aviation authority.
Town planning (in urban areas) is required. Structural integrity testing (or materials which meet this) in the case of 'raised' pads etc. etc.
Aside from the above .. your location is another important variable. Building materials and labour costs are different in Sydney than they are in Hanoi for example!
If this is not a study project and there is a 'real' requirement then the only sensible solution is to hire a qualified consultant - one who has done the job before (preferably many times) and who has a string of satisfied clients who can vouch for their work.
There is a member of our community under the username
JimL who specialises in helicopter landing areas - so you might try sending him a PM - he may also have some indicative costs relating to past projects.