New HVAC unit to 1930s rehab where none existed?

[Javier Cuevas Santos]

Planning a rehab for a 1930s 2-story 3 bedroom 1.5 bath house. Rehab is purely cosmetic and quoted around 5-7K to get it rent ready. Previously only had a ground floor furnace for heating and one window A/C unit for cooling. During inspection the furnace is found to be completely out of commission. I know I must provide a way for heating and air con in the home. Im waiting for quotes from HVAC companies but I’d like to ask your opinion. Would you invest in a complete new HVAC system and duct installation where none exists? Or start out with fans, window units and heating units? I want to minimize the risk for fires since the bedrooms are carpeted. Goal is to get it rehabbed and rented ASAP. I welcome any advice!