Andy
You haven't provided enough information to enable a proper assessment to be made, and in any case only you can decide if a particular investment is suitable for you, as only you know what your objectives are and how this property fits in.
Some things for you to consider are:
* are you wanting income or capital growth from the property?
* what type of property is it and where is it (eg 1 bed flat in London, 3 bed detached in North of England) and therefore what are its prospects for capital growth?
* have you researched this area and decided it is an area in which you want to invest in property?
* how strong is rental demand for this type of property in the area?
* what condition is the property in, and what are the expected maintenance requirements?
* what type of tenant can you expect to attract and what are the relevant licensing requirements (if any) applying in the area?
* is the £145k property value realistic? likewise the £675pcm rental?
* what other costs are associated with holding the property? for instance, if it is a flat you can expect £80-100 per month of ground rent plus service charges
* if your Plan A didn't work, how could you redeem the situation in order to minimise your downside?
* if someone is telling you this is a great deal, why aren't they doing it themselves?
* could you invest that money better in an alternative property?
Hope this helps
Cheers
Neville